This is not a comparison clip but just the Axe-Fx Quantum Recto 2 with Cab Pack 13: ML USA Bulb. I spent this day comparing Irotlas's Mesa Boogie Dual Rectifier Roadster head to the Recto 2 Red Modern amp sim (that amp sim is the closest to the Roadster) and really liking how similar they sounded.
I'm not sure if I'll have the time to shoot a video about this so I thought I'd give you guys the summarized version of me trying my best to make these sound the same with as little tweaking as possible.
-Master level needs to be quite low (1-2 and I have it at 1.5) to match the Roadster. We intentionally had the master quite high knowing that the default master setting on the Axe-Fx usually feels too high. Still around 2 is the highest I would ever go. I mean palm mute a little bit and it's really evident. Turn that master DOWN!
-Gain (input drive) at 12 o'clock is the same amount of gain. (They were not in FW19 so maybe that "too much gain on Recto 2 bug" has existed for some while now.) This control however was a bit more sensitive on the Axe-Fx. 12-3 o'clock on the real amp is close to 12-1 o'clock on the Axe-Fx. Bare in mind this might be a difference between a Roadster and a regular Dual Rectifier as well. For rhythms I suggest to leave the gain around 5-6 if you want there to be some articulation left. For leads you can go further.
-Speaker Low Resonance Frequency with a real Mesa 4x12 cab is 103hz and the Q at 1 gave me an identical low end to the Roadster. Experiment with the low resonance amount. Have it around 5-7. You want there to be rumble but if your palm mutes are over the top decrease the value. Never under 5 though. Turn that bass knob to 2-3 rather than turning the Low Resonance down.
-EQ-wise the Roadster and the Axe-Fx were almost identical once the low resonance was tweaked correctly. The Roadster has a bit more middles than a regular Dual Recto. If you want to sound more like a Roadster don't be afraid to turn that mid knob up quite a bit. F.ex. in this clip I had middle at 7 and treble at 6.5 bass at 2... Now I'm feeling like bass should've been on 3.
-My extra suggestion would be to have the presence knob at 12 o'clock and instead affecting the brightness with the bass knob and low res amount. This way you'll end up with something more authentic sounding.
Have fun with Quantum! Recto 2 Red Modern for the win!