I did some testing with thunderstore mod manager, both with mods and without. There was not a big difference between them. range from 8.2 to 12.9 FPS after about 2 min of testing.

Then I tried it with steam dx, and it was a huge improvement 10.8 to 17.4 FPS
Finally I tried it with steam Vulkan and it improved again 13.2 to 18.9 FPS

It seems thunderstore mod manager is bringing down my FPS. I had been using vortex with other games but switched to thunderstore when one of the earlier mods I wanted with Valheim suggested I switch. Now it seems I need to go back to vortex, or another mod manager, or install the mods myself.

For the people that use mods, which mod manager do you use, or do you manually install them yourself?

How does everyone launch the game, from steam, your mod manager, or desktop shortcut?

My current video settings:
Resolution: 1920 by 990 60 HZ
vegetation quality: low
Particle lights: high
Draw distance: med
Shadow Quality: low
Bloom: on
SSAO: on
Sun Shafts: on
Motion Blur: off
Tessellation: on
Soft Particles: on
DOF: off
Anti-aliasing: on
Chromatic Aberration: on
Vsync: off