I've bought Michigan Synth Works before. They are good builds and available from retailers. You can also get your micro units commissioned by private builders; but check around before you send off your money. I had a couple made from someone on Modular Grid and he did a great job and delivered as promised (actually a couple of days early).
Using an envelope inside PNW, Disting, or another module like Ornaments & Crime will definitely work. But the flip-side to that is that the envelopes are readily available for tweaking. Menu diving sucks. Envelopes tend to take a lot of back and forth depending on what you're trying to achieve (like getting that perfect pitch and decay envelope on an 808 style kick). The two envelopes in the Neutron would be okay. But it's pretty inconvenient using them and they are pretty basic. Trying using what you have at first. But keep in the back of your mind that you might want space for the dedicated envelopes. Envelopes can do more than control VCA and filter cutoffs. You'll probably want more and a few different types.