So you wouldn't use the Mosvalve for direct recording, not required or needed. Some why nots read on...
I'm not a microcab expert so others please correct me, "generally" cab sims are used between the preamp and the direct in, no poweramp involved. Particularly with ADA MP1/2 which are designed to make the entire tone and then just have it amplified (in stereo) by a transparent clean power amp (no added colour/tone, just volume).
So cab sims (eg microcab) are designed to emulate the sound of micing the guitar speakers so provide for different mics/positions/angles and different guitar speaker/cabs and turning it into a line level signal suitable to plug in direct.
Some cab sims are capable of taking the poweramp output (should you want to add particular power amp colour as well) eg ADA GCS3 has -30db input for this but it doesn't provide the speaker load the amp wants/needs so typically you'd plug the cab in as well (to provide the load) but take your direct feed from the GCS3 out.
Upside of microcab IIRC is it's stereo
and very well appointed for different cab/mic combinations. There's other threads here about it and how you can mod it into various forms of persuasion.