So not really a synth advise, but have you checked out the app Flip? It seems to tick all the boxes you want. If storage is really a big issue, this is the way to go. However, if you want to get away from screens:
They gear you mention has a pretty small footprint already. Maybe there is a smart way of storing them? Like placing them on a piece of small wood where they are detachable. Hang the wood on your wall or something. I don't know your exact situation though, so this advise might be worthless.
One general advice that is mostly true for all music gear: If you buy used, you can always sell it for around the same price again. That way, you can basically try gear without the worry of losing too much money. Buy a used MC-101, see if you like it's workflow for a month or two, and sell it again if you don't like it.
Unfortunately have no experience with the MC101. If you look at Youtube and like it's sounds and workflow, that's a good indicator. Be aware though when watching youtube stuff: You don't get the musical experience from the person you watch. So if someone makes a track you like, it is not an indicator that you yourself can make cool music with it.