I'm in a similar boat. My F4-423 will be here today and I'm probably not even going to bother with TOS. I'm going with TrueNAS instead. Unraid is also a possibility. Both are excellent, mature platforms. For most of the people most of the time, you can't go wrong either way.
TOS has had too many security issues over the last few years. Some of them are severe, like revealing the root password or automatically opening up SSH to the internet. In defense of TerraMaster, they aren't the only ones; QNAP had a backdoor for a long time as well. My problem is that if a company thinks these are good ideas, their overall security hygiene probably isn't great. I want to allow outbound internet access from my NAS so I can fetch backups of OneDrive and back itself up to B2 or S3 Glacier, so who knows what it's ingesting when it calls home for updates.
My suggestion would be to tool around with Unraid, then tool around with TrueNAS. Maybe even look at OpenMediaVault. If they meet your needs, then they're probably a better choice overall.