I do see an advantage to tie it to a time period for the customer. If it was just tied to a major version then Unraid would have to make a decision about if a feature belongs in version 8 or version 9. Essentially locking that feature behind a paid upgrade. By making the upgrade tied to a time period they have no incentive to hold features back for the next major version.
If you go with QNAP be careful with what you provide access to over the internet. QNAP seems to have security vulnerabilities quite often. It would probable best to only use a VPN to access any services/media on it.
I’ve been running TrueNAS core for years. I used to have my applications in Jails on TrueNAS. If you just want to start out learning I think using SCALE and keeping your apps within TrueNAS is a good way to go.
I believe SCALE uses docker for its apps so that should make it easy to migrate your data in the future if you pick another platform.
This works great so far for the first few checkpoints on the delta emulator for iOS.