I have the powered Kemper Rack and have been using it through my Bogner 2x12 OS using Scumback M75 PVC @ 65W. I the user category of mostly a live player, only a little recording. I Talked to a Kemper support guy who basically said that the Gemini II will blow me away, 1 because of FRFR, 2 because of the ability to use the empower technology to tune the cab to the room, and 3) because the class D amps they put in the gemini blow away the class d power amp in the kemper. He said there would be a substantial noticeable improvement. Turns out in retrospect he was the head of sales and the co owner of mission, not your typical support guy.
To my ears, the powered Gemini II did not sound as good as my powered Kemper Rack driving my Bogner 2x12 OS, regardless of how I set the empower knob, full FRFR, Full cab or anything in between. Regardless of clean, edge tones or gain tones. It was also heavier and much more cumbersome. It does not have casters, and there is only one handle on the top, but nothing on the side.
To me, the Gemini II sounded less full, with less bass response at the same Kemper setting. I was able to replicate any perceived clarity from FRFR by just increasing the presence on my kemper when using the Bogner....so if anything the experience helped me realize that I could improve my sound by increasing my presence, and after having done that, the Kemper/Bogner was way fuller and had more thump, and equally well provided feedback at will.
I returned the Gemini after a few days of trying to look for the magic.
I think it's possibly great for someone who does not have a nice guitar cab...although I reject the notion that the Gemini class D is superior to the Kemper Class D based on my experience...unless the bogner was so much better that it compensated for an inferior class D in the kemper and still sounded better than the Gemini?
Lastly as we know...it's all subjective and our ears differ...so good luck finding what you need.
I'm a Mission Engineering fan, using their expression pedals with my Kemper.