Apple watch series 7
is it recommended to put a screen protector and case on the apple watch?
iPhone 12 Pro, iOS 15
That is totally up to the individual. I have put a screen protector on some of my previous Watches. I haven't on the last two. My watches have been fine either way.
If you think that your lifestyle will cause your watch to get banged and dinged, then a case may be appropriate.
It's also a matter of esthetic taste.
M1 Mac mini, macOS 12.0.1; Watch, series 5 GPS/cellular, watchOS 8.1; iPad Pro 2nd Gen, iPadOS 15.1; iPad Air 2, iPadOS 15.1; iPhone 12 Pro, iOS 15.1; TV 4th Gen, tvOS 15.1; HomePods, audioOS 15.1 and Airport Express w/ Airplay 2