Is there still iTunes plus upgrade for DRM’ed music

iTunes Match, when turned on, actually suppresses the Store link for iTunes Plus in the iTunes app on a Mac or PC. The option to upgrade no longer appears to Match subscribers. There is no reason to upgrade. My personal old-school drm-sullied iTunes songs are now available to me without DRM through Match now that I've subscribed and synced my library.

iTunes removed DRM from it's music catalog in 2009, so I'm wondering if your question is about iTunes at all? If not, you might be better off specifying what DRM scheme you have a question about.

That said, iTunes used FairPlay for DRM before, and as explained here, it does generate a unique key for every user. So, it will indeed be different for every customer. The same should be true for all DRM schemes, since if the customer could not be identified from the data inside the DRM scheme, it would defeat the purpose of DRM to start with.

It is also worth noting that while DRM was removed from iTunes, current downloads still contain your Apple ID in the downloaded file. However, tool exists to remove this meta-data from the media.