You might want to check How can I change the location where Live TV and DVR saves recordings?.
I didn’t test it yet because I just got my HdHomeRun today, but I went ahead and created two new libraries. One for recorded movies and one for recorded tv shows. Those are mapped to a separate directory/share on my NAS and are accessed with a different user/access right (read+write) compared to my regular video/music/photo share which Plex accesses as a read-only user.
