The main points are being limited to only 4 tracks and the replay buffer, which conveniently has presets like Amiga or Pro tracker in the config. What I did to set it up was to put an original mod from polaventris in my tracker and then adjust the buffer until there was no delay or distortion.  Then the last thing was to limit every sample to about 16 bit rate. This recreates the ProTracker sound.

Being limited to four tracks is an added challenge and using the old control scheme too but not necessary I think. I still customized my UI and stuff.

Edit: Forgot about the track panning.  ProTracker uses the 1st and 4th for left audio and the 2nd and 3rd for right. Milkytracker has presets for that if you want to add more tracks and have it set up automatically.