You won’t be using a traditional RAID with TrueNAS Scale. You have a choice of Stripe, Mirror, RAIDZ1, RAIDZ2, RAIDZ3, dRAID1, dRAID2, dRAID3. The docs are very detailed, so you should read up on RAIDZ and the other types elsewhere, too.

Both Netflix and Disney+ now have “cheap” tiers with ads, at least here in Germany.

Since you only use Plex because of overseerr: There is a fork called Jellyseer that is compatible with Jellyfin. Haven’t tried it yet but it may be worth looking into.