I explored this question pretty thoroughly a few years ago, and I came to the conclusion that there are about four options:

1. Folders.
2. Fuji rangefinder.
3. View cameras and their close kin, either in 2x3 size or with a rollfilm back.
4. Monster SLRs like RB Graflexen and the Rittreck Optika.
...and I guess the Medalist, which I'd never considered because of the 620 issue.

I've owned all but the Fuji, which I handled in a store and decided against because of its size---in hindsight I'm not sure I was right.

You've pretty much constrained yourself down to a Medalist, among those options, but I wonder how solid all those constraints are. For instance, and with apologies for a kind of rude question, are you a good enough photographer on all the other axes that film flatness is a significant issue? (I'm not, and I suspect many of us aren't---of course some of us are, and for those people it matters.)

I think sheet film has fewer flatness issues than rollfilm in this size, which might actually argue for one of the smaller view cameras---a 6x9 plate camera isn't much bigger than a 6x9 folder and a heckuva lot smaller than a Fuji RF. Loading individual sheets is a bit of a pain, but then so is respooling to 120. I'd consider it in your position.

The Medalist viewfinder question I'm afraid I don't know about. It doesn't look that small to me in photos, though---remember that the camera is bigger than it appears!