I've tried it. You can amend your guide a bit if you want to as I've noticed a few things.
There's no need to start over (reconfigure and rescan).
You can carry over your layout, settings, library etc. from the non portable local install by simply copying the contents of
subfolder of the portable MusicBee installation and also copying over
subfolder of the portable MusicBee installation.
If your music files were stored locally previously (for example on a drive in your PC as drive letter G) you might have to use
File -> Library -> Relink Music File Paths...
to adjust the file paths to a network location (\\192.168.1.3\Music for example) that all the PCs you plan to use MusicBee with in this fashion have access to.
For my use case I did not even need to do that as I had mounted my music library as Z: in windows as a samba share from my TrueNAS server. Since I also created the exact same share of Z: on the second machine that I use the portable configuration on there was no need to change any file paths.
All I did was to download the portable version of musicbee, extract the archive, install it to my internal ssd, copy over the 2 folders as described above, copy the portable installation to a network share on my server, start musicbee from that location, locate the library within the portable musicbee installation and create a shortcut to the MusicBee executable location on both PCs. If I had not already recreated the Z: share mount on the 2nd PC for other reasons I also would have had to do that.
Performance via the network is almost on par with the performance on my m2 ssd and scrobbling works. Even when I start playing a track on my desktop PC and finish it on the HTPC.
Thanks for the guidance, I'm happy with the result.
I forgot to mention that if windows asks you if you want to trust the program from an unknown source when you open musicbee from the network location, you can avoid that by adding the file server IP to the trusted intranet sites.
In windows that is:
Internet options -> Security -> Local Intranet -> Sites -> Advanced -> add the IP of the file server and confirm + save