The ProTracker 2.3D clone specifically emulates the Amiga's Soundchip (Paula), which sounds somewhat different from the expected sound of a modern audio application. However, OpenMPT 1.27 will feature such an emulation as well for Amiga modules, so for MODs it will sound almost identical to the ProTracker clone.
Schism Tracker sounds pretty much identical to OpenMPT - it is based on the same original mixing code with different resampling filters, but all in all its sound is almost identical.
With this kind of vague descripting it's hard to guess what you mean by "light version". Do you have any particular modules that sound different? Can you create a WAV export of those modules in Schism Tracker and OpenMPT for a comparison?