Intel introduced a new graphics driver update containing optimizations for PC games, with a DX11 title receiving a 750% improvement
Notice it says “a DX11 title,” and that title is Halo: The Master Chief Collection. That is to say that the game likely used to perform very very poorly, and now performs acceptably.
Checkout protondb.com search for anything. Chances are just about any game you might want to play will run on the Steam Deck. Games that outright don’t work are few and far between. The exception is competitive games with invasive (often kernel-level) anti-cheat measures.
I haven’t played much of the arcade version of Contra, but on the NES version, the S can actually shoot faster. There’s a limit to the bullets you can have on screen, so if you mash the button fast enough, you get to shoot again as soon as a bullet leaves the screen. If there’s nothing to stop your bullets before the hit the edge of the screen, you’ll end up with a line of bullets in front and a spread of 3 bullets. If there are any obstacles that stop your bullets early, eventually, you just end up with a stream of bullets in a straight line in front of you with no more spread.
The laser only does 4 hits per beam, but you can only have one beam on screen at a time, and if you fire again before it hits, it just disappears before firing the new shot.