I use a Torpedo CAB in series with my Ultra when I use it's amp blocks vs my tube preamps, so I'm creating a virtual slave amp scenario (think Guytron). In this role I get most of the power amp color from the Axe, and use the T_CAB to improve feel and bloom which it does amazingly well IMO.
Note that the T_CAB's presence control works backwards to most, so use the PP tube power amp sims and start with Depth at 50%, and Presence at 100% for all tube types excepting the 6L6's which should start at 50%. With typical -3/-6 peaks on input, I run the T_CAB's tube power amp sim's gain around 8+-. Obviously adjust to suit.
On the Axe I typically don't run the master volume above 8.5 for vintage amps, and lower for higher gain amps.
For cab sims use either Axe or CAB (third party IR's for the Axe), depending on whether you need to feed FOH and a stage guitar cab simultaneously, or prefer to save some CPU etc.
Good luck...