Until I got my S8, my only previous experience with TouchWiz was with my son's S4, and S2 before that.
My previous phones were using the legacy BlackBerry OS and BlackBerry 10.
The S8 UI was a plesent surprise compared to what I'd seen on the S4. I thought I'd stay with it. I tried Nova, but decided to go back to TW. Then I got the BlackBerry Hub+ suite of apps including its BlackBerry Launcher and tried it for a couple of days.
It wasn't bad, but I went back to TW.
Then, I found out about the TeslaUnread add-on to Nova. TW does have notification badges, but not all apps are supported. The BlackBerry Hub is not, and I prefer it over the Samsung email app.
Also TW can't change the BlackBerry Calendar app icon date. Now, BlackBerry does provide a home screen widget for the calendar that does change the date, but its size is smaller than other adjacent icon, so it looks out of place.
So I tried Nova again, and found that it does change the regular BB calendar icon date.
So, I went ahead and paid for the Prime, got TeslaUnread working, and now use Nova.
The only problem I see is that TeslaUnread can't seem to get the number of unread messages right from the BlackBerry Hub. But, that's not a deal breaker for me. It shows a badge, and sometimes the number is right.