I have a Mamyia Universal with 3 lens. The only draw backs to a Mamyia Press or Universal is that you have to cock the stutter, and you have to look at the lens to confirm and change both the shutter and f stop. Most photojournalist who used any of the press type camera used a flash. Mamyia made a family of press cameras, the early cameras used a 90 and the universal uses a 100. There are 2 wides a 50 and 65, (and need a seperate viewfinder) and 2 longs lens a 150 and 250 (rather rare) which if I recall correctly did not couple to the rangefinder. Mamyia made a 127 for the Polaroid verison of the press. All of the lens are rather slow and I think I would have a difficult time hand holding a Universal at low shutter speeds as it is a rather heavy camera. And if you trying to be discrete it is a very large camera.
The upside is that with a 6X7 or 6X9 depending on the back (Mamyia also made a multiformate back with 4.5X6 6X6 and 6X9) you get a large negative to work with, so you can push your film 1 or 2 stops, or use Dianfine so the slower lens are not too much a problem.