It’s up to you. Things to consider:
- Size of data
- Recovery speed (Internet speed)
- Recovery time objective
- Recovery point objective (If you’re backing up once per day, is it okay to lose 23 hours of data when a disk fails?)
If your recovery objectives can be met with the anticipated data size and recovery speed, then you could do RAID 0 instead of RAID 1 to get higher speeds and capacity. Just know that if you do that, you better be on top of your backups because they will be needed eventually.
Most things people self host are either torrent clients, HTTP(s) or are game servers. The first one can pick a port arbitrarily. The second can do host routing. The third - some of them support SRV records so you can direct the client to an arbitrary port. It’s becoming less common to need multiple public IPv4 addresses.