About the OD in front of the amps
i have tried them all with and without an OD. To play the kind of music i play i need more attack and tightness than those amps can give by themselves.
I use the OD this way
Gain= 0
tone = mid to max
level = mid to max
and i use a little less gain on the amp, to me it sound way better for Death, Thrash, core etc. all of the heavy stuff i play in my band. The OD doesn't add distortion, it just improves on the tone you already have with your amp
Since i've shown that trick to my friend he never uses any of its high gain amps without an OD
I also worked with many good engeneers to record albums and these guys also worked with some of the best producer in the world and most of them get their recording and live tones from high gain amps with an OD and noïse gate in front of the amp. I could give you many exemples of well known metal players who do that. Even Metallica used to use a tube screamer in front of their mesas
I know some people fimd it bizzare to use a pedal with such good amps but i'm telling you, you've got to try it, you'll be surprised. But you got to use it the righ way, don't add any distortion and use a noïse gate, it is impossible to play with this set up without a noïse gate because the amp becomes uncontrolable.