I believe the Bluetooth disconnecting is a S21 series bug that hopefully will be fixed via software.I never had a lot of apps on my Apple watch so the Tizen app 'shortage' isn't a big deal to me. I do feel like the Samsung watch and phone (Active2, S21 Ultra)tend to disconnect a lot more frequently than the Apple watch and phones, though maybe that's becasue the Galaxy watch lets you know when it disconnects. The Galaxy watch seems to struggle a bit connecting to WiFi.My
The Outlook app on the Galaxy watch doesn't show the calendar whereas it does on the Apple watch. My work stuff can only be accessed via Outlook so that was nice to have when needed. I know that's a Microsoft thing but it;s something I've noticed.
Other than that I'm pretty happy with the Samsung combo.
I have never had a disconnect on my earlier S20+ with my Galaxy Watch3 but it is very frequent with my current S21 Ultra.
I have read somewhere Samsung has acknowledged this issue and is working on a fix.