People say all kinds of things.
There's a mod that'll expose more graphics options that helps a lot to fix some of the issues.
https://www.nexusmods.com/valheim/mods/351

Most of the options in the graphics menu are useless for performance, the ones that impact it that are exposed are vegetation and shadows and draw distance, the rest are just post processing and don't impact the game performance at all.

The game itself is a bottleneck for performance. I'm using an old ass computer and it can't use all my cpu or gpu and it should be maxing them out completely. But I'm just sitting around 75% across the board at anywhere between 60 and 15fps.
There's a lot of optimization left to do.