Greetings!
I have intentionally refrained from giving too much feedback or posting much beforehand because i wanted to give the mode a few tries and see some more aspects of it.
And now I am 108 games in... would you look at that. 
I want to prefix this post by clarifying something before i go on.
I haven't had this much genuine joy in Leauge of Legends since the first time Riot released URF.
It enjoyed almost all games (almost... more on this below) in this mode, because nothing felt like the round before. It was lighthearted and intense fun and i did not feel the burnout as much as back when URF was launched... going back to Summoners Rift felt weird however but that is only natural since Nexus Blitz has a increased pace as opposed to the other modes which i greatly enjoy considering you can almost avoid the early game entirely (and the boring Minion last hitting part)
But enough of that. Lets dive into this shall we?
First i want to give a bit of a overview of the mode. Then i will jump into the different rewards/events followed by the reintroduced items and lastly what the roster in general feels like during blitz.
The Gamemode
Overall i think Nexus Blitz manages to scratch the itch it was intended to. The games are fast paced and packed with intense team fights on a map that is greatly condensed.
"Sudden Death" helps basically "capping" the longest possible time you spend in Blitz so no matter what you can always say you have "enough time for a round of Blitz" if you only got half an hour. Which is impossible to do on SR since the games can range widely.
The Maps layout allows a variety of champions to shine (some more than others) as the lanes offer a wide but longer battlefield while the Jungle offers the possibility to sneak behind your opponents to ambush a on fire Squishy due to its winding paths.
The Map itself is by no means perfect in layout and it surely will go through a lot of transformations once Riot has a design/fantasy for the theme in mind. But i think it does its job nicely despite it making some Ranged champions very hard to deal with.
coughs

Death Timers seem reasonable but should be still a tad bit shorter late game i believe.
Events and Rewards
Let us start with the events themselves.
Bardle Royal / Bardle Royal Juggernaut/ Paranoia Royale: 
Enjoyable. It really helps that you are allowed to instantly re spawn (although it sometimes does feel bad if you managed to kill a lot of the enemy team before the event starts) The event is as stressful as it was intended and allows the game mode to really distinct itself from the others. While some Champions like Poppy do have advantages here (as well as most CC champions) it is a very welcome event i always enjoy having around especially if it is not super early into the game.
A personal nitpick with this event and one that (apparently) is shared in the community is that it sometimes circles deep into the enemy team. My suggestion here would be that it either only spawns on the axis of the map in the middle and only very slightly shifts to the side of the loosing team. (something you seemed to have addressed for the most part with the last update). A filter could be implemented however that requires the turret to be destroyed before being eligible for being the center, just a thought.
As for Paranoia Royale? It is the least fun event to me from these three. I understand the basic thought behind it but it is really annoying to deal with and seems to heavily favor melee type characters and bruisers (which seemed intentional) I like the fact that it forces you within closer range of your opponent, but that seems to be achieved by the other versions already in part. Maybe reduce vision range less intensely but make the circle contract much faster?
King of the Hill (KOTH) 
Also a really solid event. It does mean that the team with more AOE has a bit of a easier time but the capture mechanics alleviate the issue due to the capping team constantly taking damage as well as progress being halted if the point is being contested.
I have yet to encounter a "BS" spawn for the point as it mostly seemed fair to both sides (never directly under a turret) but there have been some instances i heard of where that wasn't the case, a kink im sure as we move forward with Blitz will be addressed however.
Push the Cart (GET ON THE DAMN PAYLOAD) 
Really fun. A event that tends to be easier for melee champions due to their larger HP pools (don't want to push the cart as a Lux for instance) but due to them being meele they are also more vulnerable to punishment in general. Really fun and neat.
However there are some issues with the Tower target. It is really silly if you almost manage to push the turret just for a cannon minion or a random auto attack to destroy the turret forcing the cart to go further in. (i do see however why that mechanic is there, just a thought) There is also a strange interaction with
passive. His passive turret counts as a allied structure so when he activates the turret as his own cart pushes by and the enemy just barely gets it, they are right under the "nearest structure". Winning the event.
I don't consider this much of a issue but its a strange interaction when it happens for the first time.
Closing thought about the cart event would be that i think perhaps a small buff of sorts could be applied for allies pushing along to incentive pushing as a full team. Maybe for each team member present people in the circle gain adaptive power for a bit. Just a random idea.
Loot Teemo / Loot Veigar 
Neat little events respectively. The idea behind them seems interesting and allows for some really stressful interactions. However there are some issues. The money it awards are ridiculous at times (see the Mundo 1k expample) and it is very frustrating if the Teemo/Veigar waltzes into the enemy jungle or even towards turrets at times. It seems like it would be fairer if they were just patrolling up and down relatively in the middle but never go into the corner of the maps.
I personally prefer Loot Veigar because of his ridiculous stuns (would be cool if he had a bar that counts down when he casts them so you can back off)
Aside the part where it wanders off into annoying directions this pair of events is really neat and tends to be fun. Im sure with some tweaks to the pathing this will be much more enjoable.
Snowball Fight aka. "DUCK FOR COVER" 
Many people have problems with this event mainly because it basically encourages you to sit back and start sniping from afar in hopes of landing that crucial snowball that wins the event. The slow chains are pretty annoying to deal with but reward for good aiming hence there is fairness in that as most of the time the snowballs themselves don't have THAT BS hit-boxes. I really love this one and wish it would come up more often. It turns the entire game into a tiptoeing game of paintball where you can even barrage on one poor unfortunate soul to unleash your avalanche. I also really love the penguins as a nice touch (I WISH THESE WERE POROS SO BADLY) cough
The Snowball Fight is really lovely and the music matches the tone. Even then, i have won many instances of that event by engaging the enemy team because most of the time they will be so focused on running away that they forgot to throw their (heh) balls while you are in their face. Consider that more of a tipp than anything really.
Scuttle Racing aka. MEEEEEEOOOOWW 
THE BEST EVENT EVER.
I dont know why... there are so many champs that are way too strong for this mode. CC piling makes the event trivial and there are a couple of other instances where champions like Poppy or Singed can singlehandedly win this event for their team but something about the event announcement? GOSH
Hearing that MEEEEEEOW sound just makes me burst with joy whenever it happens. Please consider making all events somehow announced in a epic fashion. Make it so there are like Minions with scuttle fan shirts and flags waving on left and right side of the river in the middle. GOSH dang it i love scuttle racing so much.... despite it being imbalanced based on CC but Christ i want a Scuttle Racing Team Fan-shirt at my doorstep right NOW.
Where was i...
ah yeah. Scuttle Racing. Its fun, really is. Issue being CC Stacking but that is simply a minor issue to me and does not ruin the entire event for me.
ONWARD TO THE REWARDS! 
**Blessing of
**
Reasonable Reward. Nothing groundbreaking, still very useful and not overbearing to the point where it gives the other team incredible power without conditions. I really like this one. Good thing it is not permanent.
**Blessing of
**
Also really cool reward. Has some really really sick synergies and is interesting to play against and with. Really love getting this one. Especially since its not permanent
**Blessing of
**
Very strange to play against. It sometimes feels like you are being pulled from distances or places you don't think you would get hooked at but the visual indicator showing where it will roughly shoot is really cool since you can plan ahead... also really funny if your Braum gets pulled in and ults everybody.
Generally neat and has some clear counter play behind it. (don't get hit or don't approach when its up)
**Blessing of
**
VERY powerful. It seems like its very frustrating to play against however. I would suggest lowering the time it is up for a bit. I think its okay in itself but needs some fine tuning as i said.
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