Can I use QRecall to make a non-encrypted backup of files from my home folder when that folder is open (i.e., accessible)?
In principle, the answer is yes. I'd suggest configuring the QRecall scheduler to NOT start or run actions while logged out. If you are just capturing your own documents, you probably don't even need to authenticate it to run with administrative privileges.
However, I strongly suggest that your download QRecall and try it with a trail identity key first. I have not tested QRecall recently with File Vault and Apple has made a large number of security changes that impact what applications are allowed to do under File Vault. So try it out first and make sure it works on your system.
I have a long standing to-do item entitled "Make QRecall File Vault Friendly" which has been around for some time. I've been putting this off until I add archive encryption to QRecall, which would make it much more appropriate for using in conjunction with File Vault users.
Frankly, I wish I hadn't encrypted my home folder with FileVault. I don't have enough space to un-encrypt it
If you have the external disk space, you could probably copy or capture enough to your external drive to un-encrypt your home folder and then restore the documents.