The stock rom has a video enhansment feature. Is there a magisk module for that too?Yes, you can flash it.
Yes, you can go back to stock.
No. Stock camera app only works on 9/10 based ROMS. There is a magisk module for stock camera app, that is pretty much the same, but no 960 fps, no video resolution options, sometimes flash sucks etc.
So, better to use another camera app from play store or this magisk module if you miss stock one.