EPIC amp seems to be based on MESA imo. The master volume effects the drive or gain which seems to be a MESA thing from what I understand. I've landed on this amp several times for long periods of time as my go to amp, for pure out grind!!! I just did an amp shootout with my helix to get a tone for a recording and the Epic won out over Bedonk, Archon, Recto, BE100, and 5150 (which I've never gotten to sound good at all) my second layer of guitars on the track ended up being the Mark4 lead.
I was using the Free Ownhammer IR's on the modern 00.
for the leads i'd take the BE100 as the throaty midrange cuts real nice.
BE100 is the other amp I use a lot for m patches.
I find most of the L6 original amps to be outrageously good. Litigator getting the most mentions.