It Shall Not Tick is a mod that stops entities from ticking under certain conditions. I am wondering if your mod conflicts as they do similar things?

https://github.com/nanite/ItShallNotTick/issues/26

Adaptive Performance Tweaks is not really modify any ticking or so, it's only preventing the spawn of a specific amount of entities on a higher server load. Furthermore it's dynamically adjusting game rules and clustering items to avoid higher loads.

So from the technical side I see no "conflict", but ItShallNotTick using Mixin's / Core Modding, which could cause issues in general with other mods which modding the same functionality.