Can you briefly explain what these settings do?
I'm a little unsure whether to enable them or not, so I need to ask.

1- mixin.perf.dynamic_resources
2- mixin.perf.faster_item_rendering
3- mixin.feature.integrated_server_watchdog

Can you also tell us how they work?

They are explained on https://github.com/embeddedt/ModernFix/wiki/1.20-Summary-of-Patches.