You can control the volume, feel, tone, speaker breakup, etc.
With the two channels on the PS 100 I can set one channel up focused and tight to play rhythm. I can set the other channel a bit looser with the depth up to get a better feel for playing lead.
Stuff like that. It is just fine running. It isn't huge changes in the sound. It still sounds like the same amp.
You can set it up to sound very similar to the original sound. I don't do that. I set it up to get the best results for what I am doing.