In my project.
I get smooth 60 fps even on the lowest of hardwares. But their comes instances when the frame and game suddenly jump to an enormous ms amount for a brief instance and then go back to normal. Also the game somtimes skips some frames and makes my character moving ahead jump ahead.
It happens at completely random. Weird.
The phone stays cool at all times.
By your video it looks like you are using Dynamic sky? That is costly
And also try to make your materials as much as possible unlit. There is also an option in the materials to make them fully rough and disable reciving lightmap resolution.
Also you can set minimum draw distance to static meshes.
Try to use minimum lights and if you use, as much as static lights as possible.
Use as much material instances as possible rather than making new materials.
Don’t use high resolution textures.