I'm playing with low graphics and high fps setting. Does the high fps setting mean 60 fps? I'm not sure.That's what I always say. It's just about balance if you want performance you get less Battery backup vice versa.
@Agent Lu , By the way if you playing pubg go for 40 FPS I think it's better to get stable frame rate than uncomfortable 60 FPS. if you feel heat with 60 it's good for your battery health because we don't have cooling system as you already know.
I think you have to re flash the kernel because it will be replaced with whatever the rom came with. You can actually check the current kernel on settings> about phone> android> kernel. After flashing a rom to see what it came with