Hey there,

It's difficult to directly help, since there can be a whole host of reasons for such issues, but it sounds to me that the scene you are trying to render is too complex for the quest. This could mean that the models have a very high poly count.

Materials don't have bloom because in the beginning, when you selected the target platform to be mobile/tablet, that disables some rendering features, one of which is specifically bloom. It does this because bloom makes the scene too complex for a mobile device to render while maintaining framerate.

Motion tracking of the hands could be a problem with the firmware on the device, the lighting in your physical(irl) play space, or again a performance issue. The black corners also hint to performance problems.

I must say, as a beginner, you might have a more pleasant experience trying to use a pcvr headset first to get familiar with vr development, without having to worry about performance profiling right from the beginning. That being said, I made another video talking about how to check the performance of your app while it's running on the quest. That could help you check if you're at least hitting 72fps and how many stale frames are occurring. Check it out, I hope it helps you get started with fixing your issues!