Thank you for your help I have been able to get the portables plugin working (at least as well as it can), but have found that it has terrible support for parsing metadata from flac files for some reason. Since this plugin is outside the purview of WACUP support I'm just leaving information here in case anyone in the future runs into a similar problem. The flac files on my thumb drive (even when pmp_usb is given the added configuration to read flac files) are all given the WACUP metadata of a single flac file in the outermost directory of my music folder in the thumbdrive. Even when I delete said flac, the rest of the flacs that are further nested in the USB drive are left with their WACUP metadata blank. It's quite frustrating! I have tested the same plugin on Winamp however and it does properly read my flac metadata there (v 1.6 on Winamp, 1.61 on WACUP so I don't expect the version difference is to blame but maybe?)
I don't remember enough about the portables plug-in but it rings a vague bell with some of the files processed via it not being tagged correctly which afaict shouldn't be down to WACUP doing something wrong otherwise getting metadata from FLAC's into the local library, etc would always be wrong. It might even be something that's down to how the portables plug-in copies things over that's at fault but I really don't know & this just mounts up as another reason to ditch that whole set of plug-ins.
P.S. My previous post stating that the 32 bit installation includes the portables plugin only on the portable installation seems to have been erroneous. I've reinstalled and it is now there on the main release. I swear it wasn't when I tried earlier but I couldn't tell you why. Perhaps when I looked I had accidentally opened the 64 bit release.
That is likely because of trying with the newer WACUP build & it had some changes with how it tries to get some of the installer files to resolve issues where it wasn't able to download them previously. That's the only obvious thing that I can think of to explain them appearing.