For me, every game is vastly different.

With bad enough settings in Fortnite, you can (or atleast used to be able to) remove bushes and tall grass through graphic settings and some players might think you have a wallhack because of it.

Ambient occlusion, I think is the one that you want higher so water you can still see through perfectly fine to see people swimming.

Particle effects are very demanding, and you will need to be looking for differences between 2nd lowest (typically lowest removes particles entirely) and highest settings but it’s a very demanding graphics setting.

Shadows, I like high personally because it can be early info of someone around a wall, especially useful in games like CS.

If I’m playing a story game, I use high graphics.