Hey, welcome to the forum:)
I think it’s possible.
Since they are both Midi capable and since they are somewhat different, best to use them in a ‘split’ situation. Many ways to do this, either with a DAW or with some basic software for your Mac or PC, or with a MidiPal.
Also, the synth.com keyboard and many others provide built in split functionality where you set a split point and anything played above gets sent towards one midi channel and the keys south go to another.
I think you’d do fine with a Phatty. Yes, it has one less oscillator, and filter, and more limited modulation patching, BUT, it is still a 100% real deal analog Moog synth, and the very last design by the late great Bob Moog himself. The Phatty can do some amazing bass and lead sounds, and though it has only 4 parameters to tweak at a time, the controls are well thought out and easy to understand.
I think the original question -now deleted- was “do the Voyager RME and SP work together in polychain?”.
That being said, I totally agree about the clean, easy, immediate interface design of the Little Phatty.
It only has 4 parameters to tweak at a time but I only have 2 hands, one of which plays the keyboard 
Plus with POT MAPPING, you can control several parameters of the same section at the same time, e.g. cut off frequency and resonance.
All in all, it is far less limited than it first seems.
Sound wise, I find the LP more “in your face” than the Voyager. I’ve succeeded many times to create very similar patches on one and the other, but the LP has this rawer side.