PPPlay - old style!
That said: PPPlay aims to combine a good old DOS text screen with modern technologies.
This means that there is no common playback routine for all modules - instead, every supported format has its own playback code, so that replication of bugs (yes, you read right) becomes easy. Replication of bugs is a fundamental design decision of the player: it will not expand playback routines by adding fancy things like interpolation or floating point mixing.
When there are effects for some specific format that are not in the original tracker, they will only be added when they do not change the handling of the basic effects. An example is the SC0 (Note Cut on Tick 0) effect: Impulse Tracker takes the effect into account, so that it plays as if the special Note Cut Note had been entered in the pattern, while Scream Tracker ignores the effect - this is a modification of the playback behaviour, so it will not be included in PPPlay. On the other hand, Scream Tracker did not support 16 bit samples or Stereo samples - this doesn't change playback behaviour or player logic, so it is included.
Long terms short
PPPlay sounds like the original trackers, it only mixes at higher output rates and runs on modern computer OSs.