I'm in a similar boat with the OP. I am also a new user with experience using a Redplate amp, largely for its clean capabilities, for the last year (most of my playing is live-- gigging in local clubs and private parties). I've been playing in an 8-piece r&b band where I totally rely on that big, fat, warm clean sound (which actually isn't all that clean when you push it a bit...though it still comes across as pretty clean.)
I started with the AX8 about a month ago so I'm still quite a novice. But I wanted to try it because I'm in a second band now that is doing an absolutely HUGE variety of stuff, from Beatles to 80s pop to 90s hard rock to metal. I loved using my full w-d-w rig (50W Marshall +2x12 for dry) with this band because the band is a 3-piece and the sound was utterly huge...but it's just too impractical to drag around. So something like the AX8 seemed like it might be a good compromise.
I've gotten past the "live in the room" thing that you get with the amp next to you vs. the AX8. I'm using an Atomic CLR and going into the FOH and it's a winning combination to my ears. The main place where I still haven't found the AX8 to be as good a choice (sonically) as the Redplate is in the feel/sound of the big cleans I can get from the RedPlate (I'm using a BlackLine). I'm really knocked out with the sounds I'm getting overall with the AX8 and very much enjoying the versatility and very small footprint in my car and on stage.
What I've found so far with the Fractal cleaner models (that I've tried) is that they almost all have a unnatural type of breakup...they all strike me kind of like tube amps with cold bias. The guys at RedPlate have really perfected the ideal "big fat clean" to my tastes. This is not the pristine clean of a JC-120 or something like that...it's basically a more refined Fender type of clean that still seems essentially clean, even after the wave form has started to square off. It's somehow round, rich, clear with little or no "crackle" but with a rubbery, bouncy feel. You can dig in and the notes just ring out and sustain; back off a little on your attack and it sounds pretty clean. It's a fantastic "clean" sound and I haven't found other tube amps that do it this well, let alone anything in the AX8. So, it's a very high bar, IMO.
BTW, so far I've had my best luck replicating this sound/feel with the AX8 USA Clean model. I also like the Brit JTM45, CA3+ Clean, the 6G4 Super and the Band-Commander to varying degrees. All of these others produce too much "crackly" (harsh?) breakup if you push them a bit though. The USA Clean seems to hold up a bit better in this regards. But I'm all-ears re: your suggestions. What I long for is being able to set the preset so that I can back off my guitar volume/attack and get a big, clear--but not sterile--Fender type clean that's plenty loud for comping rhythms...but still has enough headroom to produce an even bigger, cleanish tone with absolutely no HARSH breakup when you open the guitar all the way up.