Interesting homebrew, most of the game is just moving right so most of the optimization there comes from lag reduction, this game lags a lot, and killing enemies also create more lag, so wether you kill an enemy or not really comes down to checking if its worth in that specific situation, and in some cases its faster to take a hit to get a projectile off the screen faster, which is the reason a random hit is taken on the Ghostface bossfight, for example, to prevent one rogue lag frame.
Also, found a few gitches, like a double jump, tho it only gives a slight jump height increase, or a way to clip through the top of some blocks.