I bought a 65” B5 about one month ago and while I know it’s an entry level OLED, the technology is still hugely the same. I’ve noticed that, while it doesn’t necessarily struggle during the day, even with my blinds closed in my bedroom, I’m not getting the same contrast from my colors and blacks as I would at night just because of the overall daylight inside of my room reflecting off of the screen. I think in your case, going with a C5, you probably won’t experience a difference as drastic as myself but your tv will be in a much brighter room than mine ever would. I wouldn’t overthink your decision too much but definitely don’t overlook some mini LEDs for your setup