You could try setting the project properties regarding shadows & switching to classic “Shadow maps”. It should be more performant.
I’ll have to look into the red bottom warning with GC. I’m guessing it has something to do with garbage collection. If you are rapidly creating and destroying objects it will trigger stutters and garbage collection.
If so you should introduce some sort of object pooling
“Click the dropdown arrow next to Perspective in the viewport, go to Stat → Hide All.”