Thanks for the feedback, I'm glad you enjoyed it!
I've already rewritten the flashlight from scratch for the next game, there were way too many problems with this one. Still working on balancing lights and exposure because the next game has day and night cycles and there's even more to adjust regarding flare/bloom. I think most of the performance issues were coming from the camera, weirdly enough. Unity HDRP is very unfriendly towards "camera stacking" (i.e. main camera + arm camera w/transparent background), so I'm working on a solution there that will be much faster. One alternative to potato mode for now is to use a lower resolution, like 1600x900 or as low as 1336x768, because the cost is happening on a per-pixel basis.