Any reason that you didn't get 120 roll film adapters for your 4x5 and start shooting roll film this way?
One of the big differences I find when moving from camera to camera is the viewing system. It really affects how I compose, interact, etc. The 4x5 ground glass is a very specific way of composing, and the manner of shooting is very specific, i.e. slow and deliberate. A rangefinder, of any size, is a whole different game. You are not looking at a flat image. You are looking through, with a sort-of framing system of white lines. And then the Mamiya has the ground glass, but it is SMALL compared to 4x5. There are magnifiers, right angle finders, and such to overcome this.
I used a GW690 for a year or so. I first bought it as a simple 'view camera' for landscapes and such. I found that the lack of ground glass really through me off and that I wasn't really able to 'see' the image I was composing in the way I wanted. So I then used it as I would my favorite camera, a Rolleiflex TLR- slower street and urban landscape work. It was wonderful in its way- quick handling and framing, nice rangefinder, as good a framing as I need for that type of work. But for street work it was noisy as all get out, and the 8-frame thing became too cramped, so I went back to the Leica or Rollei. For urban landscape work, it was a little too sloppy since I didn't like it on a tripod but it was fun and great to carry all day, and the negatives are fantastic.
Did I mention how beautiful the negatives are from the Fuji?