There isn’t a “supported” way of doing this (we do plan on adding a backup feature) but right now you can do the following (note that this could change in the future). This may or may not work between devices because of different folder structures (you should be ok since you said your folder structures were the same) but it should work on the same device.
1) *** Make sure to unprotect all protected files BEFORE you uninstall F-stop if you ever need to
2) On internal SD card go to “Android/data/” and copy the directory “com.fstop.photo” to another location like “Downloads” or copy to PC to transfer to new device.
3) Install F-Stop on your new/wiped device but do not open it
4) Copy the folder in #2 back to “Android/data/” of the new device
Everything should be transferred.
As for your concern about losing tags, you will not lose tags (or ratings) if you save the metadata to file or sidecar. However, albums, favorites, unsaved tags and unsaved ratings would be lost if you uninstalled F-Stop without backing up the “Android/data/com.fstop.photo” folder.