Would there be a simple way for me to test this with a USB disk for backup target?
The simplest would be to add a Windows server in the VBR UI, attach a USB drive and then add a repository pointing location to this drive, but this is not the only option you have. In case you deside to us a USB drive as a repository, please, review the corresponding thread here: Veeam Backup & Removable Media (rotated drives)
maybe if I'm then going to tape it's an option?
Yes, you can either way use backup repository or existing backup to disk job as a target for backup to tape job, once the backup was created
the user guide (pretty hefty tome) and did a search here but not finding the answer.
Also there is a good online help center with the detailed description on tapes: Working with Tape Media