Best way to setup sync-to?


I’m a new Kopia user and I plan to do the following:

3 clients: 1 x Windows, 2 x Mac (Mac Studio, MacBook)
All 3 clients transfer their files to a Debian Bullseye linux server in the same local network via rsync.

I want the linux server to backup everything via Kopia to:
1 x Hetzner Storage Box
1 x Backblaze B2

and additionally to two external backup media (1 x SSD, 1 x HDD) that I connect to the server via USB every sunday (mutually).

If I create only one repository (I guess that would be the best way to do it?), what should be the default destination for it, one of the two online storage services (because the physical media are only connected once in a while)?

If it is done this way, will the sync-to process to the physical media be a slow process (because the original repository is in the cloud)?

Up-/downstream for the i-net connection is 200 MBit down / 40 MBit up…

Thanks for any hints how the best / fastest setup would look like!