• The strictest requirement for making the game run at all is your GPU VRAM. Many GPUs under 3GB VRAM (the listed minimum) won't be able to start the game or will experience crashes. However, if your game does manage to launch (a level), some of these tips will definitely help.
  
• There are dozens more options available through the (GPU/CPU/Memory -> Customize) menus and through the console, but explaining things like all 4 different antialiasing options would just bury the important stuff in a wall of text.
  
• The given suggestions mostly increase FPS at the cost of visual quality, but you can just apply them in reverse if you want to.
  
• The +/- are not precise in any way because the impact of these options depends on too many parameters, it's just a shorthand for stuff like "hey, this option could give you free FPS and you won't even notice anything changed" or "this will make your game look like a potato*, but at least it'll run on a potato*".

* again, not actual potato

The single most important option for lower-end GPUs and/or CPUs and/or people that don't really care much about the graphics. The resulting visuals will be significantly worse but the FPS gain should be enormous. To repeat, this is also recommended for weaker CPUs, we just don't have a shared GPU+CPU customization menu so it's under "CPU Speed".

Could also be named "Shadow quality". Each preset step should have a noticeable impact on performance if you're GPU bound. Potato tip: Either use "Prebaked Lighting" or set this (shb_pixMaxShadowSize) to 128 through the console.

This one is slightly tricky so please bear with me. The option maps to ren_fCullDistanceBias and the default value is 1, but if you open the options panel and change the cvar to 1 through the console you'll notice that your slider is approximately 75% full. I suggest never having it above 1 unless you notice buildings disappearing in the distance, which shouldn't ever happen. For lower configurations, sliding it all the way to the left should net you some FPS on urban levels.

This one has a weird slider, similarly to "Rendering Distance". I strongly suggest keeping it at value 1 (check ren_fLODBias) for higher configurations and reducing it as much as you can bear for lower configurations. Potato tip: Set this manually through the console to a bigger value to trade geometry for FPS even more.

Very straightforward, sliding it to the left will visibly move the shadow rendering distance closer and closer. Even high-end configurations should rarely have a reason to have this at max.

Spotting the visual difference this checkbox makes is tricky even when you know what to look for because this game has fairly flat levels. I don't think it's enabled by default for any preset so I suggest you avoid turning it on even for stronger GPUs.

Set it to "Low" and if you don't notice anything wrong leave it.

For weaker GPUs, lowering these and/or setting Render Crumbs to "Grass Only" will probably increase performance. For potato GPUs or graphics haters, set trn_iRenderCrumbs to 0 through the console and you will completely disable all of it.

Overtuned particle content may cause low fps and stutters so sliding this to the minimum might help. This is most likely to happen during boss / uncommon enemy fights, like the metal snake or Kalopsy encounters. Important - there is also a particle option in GPU Speed, but that one is outdated and will probably be removed eventually.

"Zoom" basically means low FOV. Reducing this will significantly degrade most environment visuals for such scenes (e.g. scoped-in sniper rifle) for a significant FPS increase in those scenes. Note that the same option is found under GPU Speed - they're bound to different cvars, but essentially only the lower one gets applied, so just ignore the other one.

In case you have a lower-end GPU in terms of our requirements (<3GB VRAM), the game may sometimes malfunction if it tries to upload too many graphics resources. This is way easier to detect automatically than the GPU/CPU Speed options so the autodetected preset should be good enough in most cases. If you experience low VRAM issues make sure everything is set to Lowest.
For higher-end GPUs the game should already set all GPU Memory options to their maximum presets. If you notice ground textures streaming in make sure that (GPU Memory -> Ground Cache Capacity) is set to Ultra, and also read the "Ground Update Speed" tips mentioned elsewhere in this post. HOWEVER, if you notice non-ground textures streaming in (buildings, enemies, etc.) you may want to modify "Streaming buffer size" through the console using res_fBigResourcesLimit. The cvar is capped to ~8 GB and the exposed option is capped much lower.

Unfortunately, there is no "really nice trick" to fix stuttering or FPS drops because when we find the cause for a specific stutter we try to fix it ASAP. Therefore, we greatly appreciate any screenshots/video/description or any other reliable way to reproduce a stutter. Here are some options that may help with stuttering in various circumstances.

"Debris" refers to falling objects that spawn when a model is (partially) destroyed. Reducing this to Lowest could help if your stutters occur after destroying complex geometry like trees and town architecture (usually mech gameplay).

"Dynamic decals" are bullet holes, blood, explosion marks, etc. Disabling this option could help if you experience stuttering during fights that spawn a significant number of these effects.

These options control how much "ground" can be generated in each frame and they can affect: FPS, stutters, ground "streaming". If you experience stutters while running around (out of combat) try tuning these first. If you have a lower-end GPU definitely reduce the Action version completely. If you have a higher-end GPU and you notice the ground "streaming" in (increasing in resolution) during gameplay, increase these.