How much is actually changed in preseason?
Never been in a preseason before, sorry. How much is actually changed from now until the official start?
Never been in a preseason before, sorry. How much is actually changed from now until the official start?
Well, as for a starter, games are right now ended much faster than it should be, there's a new objectives that spawns when the minion spawns, and despawns at 20 minutes called the rift herald.
A bunch of marksmen got reworked.

There's also a bunch of new items, and reworked items, that you should read upon because it's too much to type up here, but I'll give you a few examples. There's a bunch of new starting items, like the Cull, where once you get 100 cs, it gives 300 gold.
They also entirely removed mana potions, and removed stealth wards to be purchased as singular wards, you can still get them by your trinkets, or by sightstones, also, sightstones build into 3 bigger support items so it doesnt take up a whole slot.
And there's a bunch of reworked AD items, primarily crit and attack speed items.
There's also a new mastery system, where you can go off of 3 trees, Ferocity, Cunning, and Resolve, where you go down a skill tree, to get one major 'keystone' skill. I'll give you an example, one of the main keystone skills for the Ferocity tree is "Warlords Bloodlust" In which critical strikes heal you for 15% of the damage dealt and grants you 20% attackspeed for 4 seconds, with a 2 second cooldown.
And those are the main changes, they're all subject for change, though.
peace [slayer-jinx-catface]
Not much, really. The new minions will kick in next patch. Other than that, they may make one or two big adjustments, but it's mostly going to be numbers adjustments from here on out. Which will still majorly change how the game feels, mind you.