I don’t have my Apple Watch 6 anymore. I’m using a Garmin 255 watch. I just use regular bands. I primarily noticed it reading low if I was doing something like sprints, hard rowing efforts, or strength training. It’s possible a sport loop would help but my understanding is a heart rate strap is always more accurate.
Not too worried. The Apple Watch was nice but the only thing I miss is being able to respond to texts which I only occasionally do and apps to show sports scores. I like the Garmin battery life much better. But in a few years maybe I will switch back if the Apple Watch has significantly improved battery life