That's kind of surprising, I'm testing on Ryzen 3900x and RTX 3060, so a very similar setup, and running at completely stable framerate. I don't think it's the 2070 Super that's causing the issues, tho maybe look into updating your Nvidia drivers if you haven't in a while. I'd still be curious about other browsers though. I'd imagine it might be Brave's fault, but ... one never knows.