The documentation is slightly out of date, the current version used in 64-bit Plus installers is 2.3.2, I don’t think there were any issues locking Plus to that version, so I will look into updating to 2.3.7.
Plus can be compiled with 3.x support (specifically 3.0.3), however it wasn’t included in the packages due to 3.0.x versions not supporting OptiTrack Duo/Trio cameras. It looks like support for USB cameras was re-introduced in Motive 3.1, so it would be worth trying again.
There is currently no support for VICON systems. This was first brought up in 2018, though no-one has contributed any implementation to Plus since then:
Real-time tracking with Vicon - #7 by lassoan.