I have the original Powermaster on my layout (as well as a TPC400), and I don't run conventional much, but my Powermaster has a problem only with PS1 units, and it will run these - but the Proto-sound portion is quiet or funky in its nature (crazy chuffing; bell/whistle confusion or silence)
My experience, further:
The TPC400 will run PS1 just fine.
The old Powermaster and TPC400 will run PS2 and PS3 just fine. I don't have much PS3.
I have a couple of old, old PS1 locos still not upgraded to ERR - Premier ATSF 4-8-4 and Southern Ps-4 4-6-2 - that will run only on a Lionel Post War transformer, regardless of the throttle (P'master/TPC400). They won't even run on a Z-1000 using the Z-1000 throttle. Lionel 1033? Fine.
This whole area of early compatibilities is rife with variations.