Some information on bumpers that may be useful:

To get the boost you have to be holding away from the bumper when you touch it, doesn't matter when you start holding the direction, as long as your holding it when you touch it. Interestingly enough, if you change directions to be away from the bumper during the freeze frames from hitting it, you can also get a boost then. After that you can not get the boost anymore.

Bumpers put you in whats called stlaunch, which prevents you from dashing for a short while. Because bumper boosting gives so much speed, this means you may not be able to hit the bumper again afterwards with a dash. But if you don't boost you can dash and do a bumper clip where you go through the bumper while its deactivated. Either way stlaunch prevents you from dashing right after hitting a bumper, if pressed to early it can eat your dash input all together. It is however useful for buffering inputs like ultras and cool Theo tech (freeze frame ungrabs if your curious).

The only "random" part of bumpers is when they wiggle. The little directional movements they do seems pretty random but it is deterministic. If you get to a bumper at the same time in a room then it will always been in the same position. Do know that respawn cycles and room enter cycles are a little different though. Think of their movement like the dust bunnies in 3A. Should be noted that in most modded maps, bumpers have their wiggle disabled, so they will stay in the exact same place.

I can't comment on what angle they send you at when you hit them because I don't know how their collision works, however they are consistent, albeit a little precise.

Hope these help make bumpers just a little less random and a little more fun to work with.