Glad to help :)
Let us break down the descriptions of Frames, Linix and Quadra but first, do you have a good understanding of envelope stages Attack, Decay, Sustain and Release (ADSR)? Its vital that you grasp of these.
Also here is a great breakdown of Maths which I did not make: https://www.muffwiggler.com/forum/viewtopic.php?t=63068 , I know you were having trouble with it, no worries, its insanely deep. I'd advise tackling it later. Check out the DL-able PDF.
Here's the description of the Quadra: "Quad Envelope / Function Generator". Check out its tags and manual too.
So the Linix is a VCA mixer, cool. Let's look at the description and make sure we understand its function to avoid disappointment and wasted time. Hmm right off the bat, its described as a solely Linear VCA. Why does that matter again?
Frames is indeed a VCA but like most of Mutable's stuff its a digital Swiss Army knife loaded with alternate modes and functions. Its a bit complicated for a rack with no simple utility VCAs, IMHO. Undoubtedly a cool module, but I get the feeling you are picking these modules because they are cool and rated well, not because you understand what they do.
Since your rack has changed too, let me start from square one. You've got a really good place to start with Atlantis. Remember Atlantis is a complete pre-made voice in a box. It has all the basic building blocks of (subtractive) synthesis: Oscillator (VCO), filter (VCF), VCA and Envelope. Also the MOD or LFO section. Therefore, its the perfect thing to teach yourself why each component is important. Experimentation + Google and I am confident you'll make sense of this in no time, especially since you have made it this far.
Otherwise I'm afraid if you keep buying cool stuff without understanding it you'll end up with an empty wallet and a meh synth. Don't worry though! You can resell modules for only a little loss.
So to start, patch this:
Metropolis gate out -> Atlantis envelope gate in.
Metrop pitch out -> Atlantis VCO 1v/oct in.
Atlantis final out goes to uJack in, which goes to headphones/speakers.
A sequence running on the Metrop will now gate the Atlantis' ENVs and send pitch per step. Funky time!
You're ready to go. Do some googling and have fun with it. I think if you stick with just the Atlantis and understand it you will begin to see what your rack needs next. Read descriptions, download manuals and watch youtube and soundcloud demos! Good luck and keep asking questions when you get stuck!!!