Optimisation question : Limiting FPS


I’m trying to get my head around optimising the FPS for my game. I had a few questions.

Question 1) is limiting FPS from the console the correct way to optimise?

When I limit my fps to 30fps (t.maxFPS) my GPU utilisation (from task manager) goes down from 60% to 25%. I thought this was ideal but then I noticed that with stat.gpu [total] goes from 11 to 14.

Question 2) When limiting FPS, Why is GPU utilisation going down but my stat.gpu increases according to Unreal?

Question 3) Should I use the project frame rate settings (shown below) instead of t.maxFPS?

Thank you.