While the Windows client is minimized and off screen, it will peg my video card to ~99%, wasting power and producing excessive heat, if the game client is sitting at the login screen while minimized. If I maximize the game client, the load on my GPU becomes normal.
After a bit of testing, it looks like the game client is vsynced to 60 FPS when it is displayed on screen, but the 60 FPS limitation does not exist when the game is minimized off screen and no longer displayed.
The login screen is also very easy to render so the virtual FPS goes up (over ~1000 FPS) until the GPU is maxed and the CPU runs very high at that time as well. This is probably not good for the life of my GPU given how often I've played and left the game running in the background but I hope that it helps others who may be experiencing this as well.
I first noticed this when my CPU and GPU fans would activate at their highest speeds for an extended period of time. I didn't think much about it until the room started getting hot with the recent heat wave here.
Note: I only have a Geforce GTX 1660 Ti because I haven't been able to get an RTX 3000 series online yet, but I bet newer GPUs would chew through this and waste even more power and heat than I.
I hope this helps others.