Starting off with the primary display thing, that is kind of a fucky thing with Nvidia at least (can't remember how it was with AMD). On my 1050Ti I want to say the ports in order from 1 to 3 go DisplayPort, HDMI, and then DVI. So even though my main monitor is in fact DVI, my TV connected to DP ends up being the primary, so if I ever have to muck around before Windows starts I need to use it, which is rather annoying.
Anyways, first stop would be playing around with your TV and checking for anything relating to overscan, PC mode, or game mode. Had a similar-ish issue on my dad's living room TV (an older RCA fwiw) and changing that HDMI ports' name it to game mode fixed the issue.
Another thing that could help (even though it's not ideal) is messing with overscan in the Nvidia Control Panel. I believe this is the right area to do this kind of adjustment in, but I'm not able to check for myself since I don't have this issue obviously.
Saturn420 reacted to flibberdipper in Resolution on second monitor being extra funky despite being set to the correct one
