I would recommend backing up the database for sure.
I don’t do that myself but mostly because I rely on embedded metadata (in JPGs) and sidecar XMPs (for the rest).
I am not sure if it is possible to install a 2nd version of digiKam on Windows because the installer always asks to remove the previous version. However I am pretty sure that if you copy/rename the folder digiKam installed to it will work just fine.