One backup on site on a different medium
One offline backup.
Backup on a different medium is archaic advice unless you’re willing to fork $$$ out for a tape drive system. DVDs don’t cut it in the era of 20Tb HDDs. I’d argue that HDD is the only practical media currently for > 4Tb at less than enterprise scale. Backblaze might be considered a different medium I guess.
Sure, but the point of an offline backup is to disconnect it when not in use, rendering it immune to ransomware, accidental deletions, lightning strikes etc. Plug in every week or whatever, do your backup, disconnect, sleep easy. I use an external usb hdd caddy (note that one needs a firmware update to work with bigger disks)