How to Boost FPS
This is the only performance guide that actually made a difference for me and helped me get the game to a point where I can play it comfortably.
The most important thing he mentions from my perspective that I haven’t seen anyone else talk about is the setting for increasing the Geometry Cache Limit in the advanced graphics settings to the max of 4GB.
This completely solved the problems I was having with lag spikes. I highly recommend checking this guide out.