In Big Sur, the combination of VEP 7.0.1056 or 7.0.1120 with AU3(Beta) client plugins in Logic Pro 10.7.1 has deteriorated into seriously buggy behaviour, compared to VEP 7.0.1056 with AU3(Beta) client plugins in LPX 10.4.8 in either High Sierra or Big Sur.
For example, now only half of VEP's total of 48 ports per instance appear to respond properly to MIDI Note-Offs; in the other half all notes hang.
According to my tests, the afflicted port numbers are:
5, 6, 7, 8, 13, 14, 15, 16, 21, 22, 23, 24, 29, 30, 31, 32, 37, 38, 39, 40, 45, 46, 47, 48.
I'm also seeing strange behaviour in VSL's AU2 workaround multiport template for VEP/LPX, when using Logic 10.7.1. For example, after responding correctly to a single Note-On and Note-Off in a MIDI region, the template in Logic then sends endlessly repeated Note-Offs for that note, separated by the original note's length it seems. This spurious repetition continues even after I disconnect the Multi Instrument from the Transformer that prepends the port code to each MIDI event! In 20 years of working in Logic's Environment I've never seen brain damage quite like that. Also there are spurious bursts of Note-Offs when Logic's Transport is started or stopped. These strange things don't happen with the VSL workaround AU2 multiport template in LPX 10.4.8.
VSL Support have responded to my report about the AU3 behaviour mentioned above, by saying that it's still Beta; which is fair enough. Many bug reports now being prepared for Apple.
In short, when using Logic 10.7.1, it appears there is now no properly workable multiport template configuration option at all for Logic/VEP.
One thing I can do now - go back to bed! Lol.