I think you've got a solid setup going on, huge props for that. Unfortunately, Qubes OS isn't for me. It wasn't designed to take advantage of graphics cards.

I also rather not carry around extra USB flash drives, which are just more devices to worry about securing and managing.

I prefer to store all my files locally on my phone and laptop's internal storage, with the disks encrypted. My files are synced across both devices using Syncthing for convenience. If I ever need to wipe my #grapheneOS quickly, I still have the files on the laptop, and vice versa, including full backups of their settings and configurations. For critical data, I use VeraCrypt, there are Android apps that allow me to access them as well.