The IC of any cab/load will change how the amp reacts. So, lets say you're using your amp with the LB2 and love the tone, and then want to make an equivalent sound on the Axe: You would match the impedance curve (LB2) and then dial it the amp block as close as you can. After, you would do a tone match (in between the amp and cab) to squish out any eq differences. Realistically there's no rules, this would be more for the specific case of amp matching I think?
In my case, all of my amps are going into suhr reactive loads (2 for stereo, more is more!) and then into IRs in my DAW (which i capture later, to load into the axe). The amps I'm using for recording I would never feel comfortable taking live (old plexi, old iic+) so it would be nice to capture even how my amp is 'seeing' a load, since that's my baseline for dialing in the tones. As I said in my original post, I don't really have too much trouble doing this matching with just the amp block settings and no tone match, but IC+tma would be even closer.
