Long, short story:
Am bad-to-average FPS gamer, looking to improve. Saw an OSU! gamer flinging its “shots” left and right and tried my best to mimick the experience in an FPS. And it worked significantly – all of my shots felt more “secure”, even with my aiming being rusty beyond belief.
And the “trick” to do this is simply leaving your “aiming hand” to aim (ONLY) while leaving your “non-aiming hand” to shoot and everything else. That’s it.
I hadn’t seen ESDF in FPS, I personally used to use it in WoW.
But mousewheel scroll is actually a great jump bind for when you precisely need to input the next jump action to time it with the end of the last. This is less an FPS thing and more a movement thing. Spacebar (or other buttons) will only work if you hit it at the precise time, while mousewheel is a lot more forgiving, since it is multiple inputs in quick succession, kind of like the rapid-fire macros. Like I suck at bhopping for example, but I could do some easy bhop sequences in cs 1.6 with scrollwheel, there is no way I would be able to with spacebar.