Do know that supports make a huge change in the lane, and not just the marksman you pick.
But otherwise, Twitch comes out strong against a Kog'Maw since his marks will and always help him in duels.
(Plus he can end teamfights faster than a full 6 items Kog'Maw)
"Why Twitch?"
Here's a complete reason why ,
Kog'Maw is more of a right clicking champion when it comes to team fights,
sure he has 2 skills that gives him peel advantage in some sort of way.
But he's more of like mechanicing an Ashe, you gotta be real careful with your positioning, or else you get punished for your wrong doings and you have no escape on doing so, other than your flash.
But Twitch, that changes everything!
(He can end team fights faster than any marksman can.)
You can stealth with movement speed from the stealth buff, and it gives you a free attack speed buff after the stealth ends!
The stealth lasts up to 8 seconds with a 16 second cooldown.
With that stealth, you can position anywhere you want without any consequences!
(That is if the enemy hasn't used
in the specific area you're in) >.>
His Passive + E is the reason he's such a scary champion, since he deals a ridiculous amount of true damage.
His ultimate guarantees him a safe auto attack range that gives him additional a.
I'm not gonna teach you how to play him, but there's a reason why Twitch isn't played often.
And that's because he gets bullied very easily during lane phase.
TL;DR
Kog needs a team to peel, has great poke / siege / tank shred.
Twitch needs less peel and has better "burst" during team fights with his ult.
"So who the fuck has the better lane phase?"
- Twitch. (He really needs items to do good though, just remember that before you try to duel anyone that's above your level.)
But as I will remind you again,
"Do know that supports make a huge change in the lane, and not just the marksman you pick."
Source : I'm currently Diamond IV in Solo Q, I also main both bot lane roles.