If you need a board with more than one network interface you could look at an ESPRESSObin: it has three gigabit interfaces, 1/2GB DDR3 memory and an ARM Cortex A53 processor. It is really small and cheap.
I’m running pfSense on it, bonding two interfaces, and using also as a VPN.
I am using the espresso bin as my main router as well, running openwrt. I don’t how’s pfSense support on this SBC, but openwrt can max out my uplink with wireguard.
pfSense support is still really experimental due to the lack of hardware support of FreeBSD systems.
A USB drive, a home NAS and a storage VPS from Time4VPS (60€/1TB/y). All the backups are handled with BorgBackup
BorgBase also seems like a great option:
My backups take up only ~7 GB so far with BorgBackup, so IIUC I would be fine with their free trial, and start out paying ~1 cent/mo.? No transfer fees, compared to B2.
I think that you have to subscribe to one of their plans such as the $25/100GB/year and every additional GB will cost you 1 cent/mo
Yeah, I’m not sure. Haven’t yet found a way to contact someone there.