Gaming nothing will touch it. I have a 55” E8 and it’s on another level to any tv or monitor out there. Picture quality, hdr, clarity is stunning. I’d imagine it’s even better with 4k 120hz (mine is limited to 4k 60 or 1080p 120 however it just gets used with a controller as it’s a decent distance away).
Burn is a possibility and for me personally I’ve put probably the same amount of gaming and tv/film hours without any issues. So ideally it’s use really needs to be at least varied to some degree.
I’d be a little worried running one 24/7 as a monitor unless you plan varied use, however I have considered getting a 48” for just that. Little to big for my setup though I think.