Hello there @Lee_Addyson!
From your information provided so far, you already are on the right path. I would suggest using further options from Unreal Insights, tracking memory use, checking for garbage collection events, increasing cleanup frequency, and reviewing object lifespans in your scene:
As for mobile specific methods, besides texture size and LODS, please make sure that texture streaming is enabled and optimized for mobile:
You can find further methods for mobile optimization in the documentation below: