My recollection is that the SW60XG was the ISA card version of the DB-50XG which, as its initials imply, was a daughter board. (It clipped onto the Sound Blaster card SB16.)
Therefore I believe it was XG version 1, referring to the wiki spec you posted before.
The MU128, a later sound module, was the boxed version of the SW-1000XG, and therefore XG level 2.
What made it great was that it could host up to three PLG cards internally, e.g. PLGs AN, VL and DX.
The MU1000 and 2000 were level 3 XG sound modules (never sold outside Japan I believe, though they can be had used) in the same case as the MU128.
They too could host PLG cards and also had USB (version 1.1(?)) MIDI (audio???), and a fibre optic audio output.