Hi.
My Cloudron server, which is hosted by Netcup too, is using at this moment 73GB and it has 14 apps installed.
For backups I'm using IDrive e2. I don't know Wasabi, but e2 is amazing and very cheap. This month for example I used a total of 409GB and they charged me $1.64. I'm using it for a year already.
Each backup is taking about 40 mins and generates a total of 24GB. I have both tarball and encryption enabled.
I think using tarball would reduce a lot of the time to backup your system and the size of the snapshots too.