i am also a Game Developer and from my side Unreal is the Best Gaming Engine to Develop Mobile Games.
As Unreal Engine is one of the most famous, preferred, and latest game development and supporting Engines that But this Might be said by every other game developer.
UE assures higher compatibility and support and eases development, making it possible in just a shorter span. All these facilities and support assistance of Unreal Engine(Unreal engine games) makes it a better option for game development by both indie and large-scale developers.
At the Asset Optimization Link of Unreal Engine, It is already defined that:
Unreal Engine offers tools like automatic LOD (level of detail) generation; jacketing and defeaturing, which eliminate hidden surfaces and unnecessary details; and the Proxy Geometry tool, which combines multiple meshes and their materials into a single mesh and material.
These all might be helpful for Preparing and optimizing a complex model for better real-time performance
But When I was doing some research on Games With Better Real-Time Performances I Got a Game App Studio Who Already Discussed Some of the Best Mobile Games Made under Unreal Engine