I've owned several medium and large format cameras, and know the RB67 well. For a medium format of 2 1/4 x 2 3/4, it's a tank. It's pretty large & heavy compared to most Bronica, but it's been years since I've used either. I can't recall Bronica models, but most it seemed are 2 1/4 square, but don't hold me to it.
4X5 is probably the most common size for view cameras, and should do much of anything you'd ever want. There's a lot of forums on the net you can find by using search engines, and typing in "View Camera" or the name & model of any camera for it's specifics. A great place to find used ones, and compare prices is
http://www.keh.com before you decide. And an excellent source for sheet film is B&H or Adorma. As Rene points out, it can become expensive shooting large format but they offer wonderful perspective control with their tilt/shift, rise/fall abilities which you won't find in most medium and small formats.
I've owned a couple of 4x5 Field Cameras and a few view cameras. Field Cameras are not going to offer as much control, but are much easier to take along. Although I wouldn't call any camera using a bellows the most portable. The difference between them & View Cameras is the way the bellows is held in place. A view camera runs along a rail, and is held in place by brackets which allow your adjustments. A "Field Camera" such as the Graflex has the bellows mounted on top of a flat platform. While it offers some movement, it's limited by comparison. You'll need also, to figure in the price of film holders, and processing needs such as tanks, and reels for developing since each format varies.
If you want to use one enlarger for all the negative sizes, you'd need to get one which is able to enlarge an 8X10 inch negative as said, along with different negative carriers,
and lenses with lens boards to match the film size of each format. And depending on which one you purchase, it's possible you may need other additional accessories. And of course, space might be a consideration along with price when needing such large printing ability.
Here's a good site you might look through for starters:
http://www.luminous-landscape.com/revie ... view.shtml
Good luck, and happy shooting.