Lot to unpack, just a quick answer:

1. Don't do that, forget the USB hub it's unreliable, if you absolutely want to go with the USB route get something like a HDD multi bay enclosure: https://sabrent.com/collections/hard-drive-accessories/products/ds-sc4b But if you don't want to fiddle with things get a ready made solution (qnap, synology, ugreen, etc) you get the hardware and the software, just insert the disks and you are ready to go.
2. If you are doing DIY look into ZFS, or use the solution from the software you are using, Unraid for example.
3. The usual advice is to do the 3-2-1 backup (three copies of your data across two different storage types with one off-site), but entirely depends on you and your data, keep at least a separate copy of your most important things.
4. Sounds good.

It's lcd with some matte finish, far from eink.

For free you say?

Can we get a few screenshots or a demo acc?

OP edited the post.

You should just link the github/gitlab/etc with screenshots.

No one will watch 40min of whatever video.

(If you are farming views then I understand why you did it this way.)

Impossible! Then why the revenue is dropping!?! Surely our political mess...i mean highly sophisticated artistic stuff is in demand everywhere!

Yes.

https://en.wikipedia.org/wiki/Wi-Fi_positioning_system

You will need to take care of the neighbors, they know...