> I don't know you, but my cloud storage is living

But you're probably changing less than 1% each day. And new changes are likely already in the cache, no need to download them.

> if the software can't smartly ignore files, it'll

Backblaze checks the modification date.

> GPON (Gigabit PON) is asymmetric. Theoretical limits is 2.4Gbps down, 1.2Gbps up. I have 1000Mbit/75Mbit at home.

2:1 is fine. If you're getting worse than 10:1 then that does sound like your ISP failed you?