I think there is no simple answer to that, the amp in the room and the far field topics are beaten to death here on the forum, elsewhere on the net, and discussed by people much more knowledgeable and educated than me,
but:
from the Axe FXIII manual .p33
grid space and cable is stereo. You don't need separate left and right paths!
from the Axe FXIII manual .p35
on the Axe‑
Fx III grid, each component is STEREO. Shunts, cables, and most blocks are stereo in/stereo out.
The grid allows up to six full stereo paths, and you do NOT necessarily need to create parallel grid paths for stereo!
Some blocks internally process audio in mono (such as Amp or Drive) but even these generally have Input Select and Output Balance parameters.
from my part, I‘ve never seen stereo IR
may be, because we listen to the sound with two ears
and we need two audio signals (A = L & B = R) to have a stereo field perception
http://wiki.fractalaudio.com/axefx2/index.php?title=Impulse_responses_(IR)
http://wiki.fractalaudio.com/axefx2/index.php?title=Mono_versus_stereo
Axe FXIII manual : Cab block diagram .p66
http://wiki.fractalaudio.com/axefx2/index.php?title=Impulse_responses_(IR)
https://en.wikipedia.org/wiki/Stereophonic_sound
in this case, once these irs are imported into a stereo cab block or into two cab blocks, with the right pan setting, I think you will get two identical monophonic signals, because the Irs obtained with the mix generated with CabLab, will be the same,
From my understanding, there isn’t stereo mix, cause you can only obtain a « mono » IR?
so, I think you will get dual mono (twice the same audio signal)
there is so much to discover and experiment with our Fractal gear!
so much, that we can forget to play the guitar!
especially when you're a bedroom player, like me
for now, I will try to use "far-field IRs" to setup amp! (like stated by Cliff)
good luck.