At best it will add whatever the extra hop is and any network congestion. My VPS host is 2200km away. I should find a closer one… but it adds 160ms with some spikes in the 200-300 range. This is round trip 4400km roughly All things considered not too bad. My VPS is a 1vCPU, 1GB ram, 1Gbit unmetered, only as wireguard server. Hope that helps.

I’m in the same boat so I setup a $2.50/mo VPS and that’s my gateway. It took a little bit to get the nftables on vps to work right. I’d recomemned tailscale or similar if you want easy, though I’ve not ever used them myself.

Syncthing is great for mirroring files across any number of devices. I use it and love it. Just remember Syncthing itself, is not a backup solution.