For most people that get low perforamnce even with beafy PC's and for people who try to get better performance from lower settings but still see no difference in FPS.
Recently, from a video i saw about fixing FPS in the game, the video creator mentioned that you need to restart the game for some of the effects to work( i know its common sense but i never tried that :V).
After trying the tips from his video i actually saw improvement on laggy maps like backlot/crash. On average my FPS was 30-45 on these maps ( jumping from low 30's to 90 fps all the time). After playing around with the settings my performace grew more to average 48-60 fps ( at some spots like backlot second flore with the LMG going as low as 44fps) but its better than getting 30fps at most spots on the map.

Link to the video: https://www.youtube.com/watch?v=DycWBQ2HGZw

PC specs:
CPU: AMD FX-8350
GPU: AMD R9 390
RAM: 16gm DDR3

Hope this helped someone. I have been seeing people saying " OMG I RUN i7 AND GTX1080 AND STILL GET ♥♥♥♥ PERFORMANCE " So for those people i hope it helps :D.