F6-424

I went from Synology to Unraid, and it's been great. (Synology had some drama where at one point they said people will need to use their branded more expensive drives and then walked it back). Since you said You have about 7TB I would plan to have around 14TB or more of storage to have enough space

I’m new to nas etc so the second half of what you’ve written is like Greek to me, however I just purchased a Terramaster f6-424 and it seems to me that the three things you’re looking for are present. Btrfs support. Support for different size disks concurrently, and ability to add more, larger disks

I have two Terramasters on Unraid, F4-424 Pro and F6-424. They run just fine. Install the Dynamics plugins a you are all set. Tip: use the same USB what come with the Terramaster systems, they last longer I was told. No BIOS fiddling needed.

I want to preface this comment with, "I don't know if I can recommend what I'm about to say to a complete noob" however, I highly recommend ditching Terramaster's software and running something different. I have the F6-424 Max as well and I'm running UnRaid on it. Aside from a couple little quirks g