Hopefully tomorrow morning will see the One UI update OTA for these devices... I've always done a Factory Reset whenever I Flashed a new Rom & Same with ANY Android Version update (I'm NOT talking about Security Patch OTAs). Frequently we see that some people are complaining about issues after an Android version update & while it's reasonable to expect that Samsung has finely tuned the OS update process - I don't leave it up to them - Knock on wood - But I've never had any issues after an Android version update - I attribute it to always performing a Factory Reset - BOTH before I download the OS Update & After I have installed the OS Update.... Just Backup your device with Smart Switch & move everything you want or need from internal storage to your external sd card or computer BEFORE you Factory Reset.
Whatever you choose to do is obviously entirely your choice - But I WILL be performing a Factory Reset tonight 🐧
Always do the same as well for the major version updates. I'm just OCD like that and like to make sure things run as smooth as possible. Will be doing this for my wife's S8 as well after I finish with my Note8 update.