Thanks to AkaGloomy on the vonMods Discord, here is some advice on how to run Mechwarrior 5 + vonBiomes well on Steamdeck and other lower end performance hardware/PC. With it, the game runs on 60FPS and 45-50 FPS in larger scale battles.
1) Use the "Loseless Scaling App"
It is an advanced solution for frame generation and on low performance hardware a big help:
https://store.steampowered.com/app/993090/Lossless_Scaling/
2) Adjust your Mechwarrior5 settings and the mod options
Settings in Mechwarrior 5:
and vonBiomes Mod Options:
I hope that helps!