For many years now I have kept my data sync'd across multiple machines by maintaining one inclusive data directory which I call dbox.sync.mir stored on the local home-drive directory of all my machines. In other words if my fossapup64 system directory is sda1/fossapup64, then the data directory is sda1/dbox.sync.mir. Before shut down, moving to another machine at another work location I run grsync to a usb drive and sync the files on the sdb1/dbox.sync.mir.
I've also stored a lot of backup system directories in the dbox.sync.mir, for instance, profile folders for librewolf, xfe, rox, etc.
It finally occurred to me to take @mikewalsh's portable approach and symlink the actually profile locations to the data in the dbox.sync.mir. It seems to work well. In one sense it's kind of like the puppy approach of having an external user/root file or directory which is then mounted. But in this case it's just a symlink. To be safe, I leave a renamed backup copy of the original application directory in the system, then copy the original to my dbox, and symlink. That way if my dbox data gets corrupted I can rename my backup folder in the system directory and keep working.
The result is my various applications remain consistent across multiple devices because they are sharing the same config files.
There's no real question in this post. But comments and suggestions, or warnings, are always welcome!