I use just the 2x3 "press" cameras, as the 4x5 is a bit bigger than I want to carry. The Century, and my favorite, the Crown, both usually have the Graflok back. That makes using a rollfilm back very simple. I have a modified Busch, and the work necessary is pretty simple. The backs and inserts can be found without too much difficulty. The cameras themselves are fun to use, but require more steps (pulling dark slide, focusing that checking view, seperate speed/aperture, etc.) making the photography more deliberate. After some time, things are either pre-set or become more or less automatic.
Since I don't use 4x5, and the 100-105 lenses are just slightly tele using 120/220, I'm right where I want to be image-wise. The usual 135 lens on a 4x5 gives a more pronounced telephoto effect than I generally want or need. Also, the backs for that size seem slightly more expensive and hard to find.
The Speed is a very nice camera, but there is more weight involved, and the shutter may not be very accurate, condiering its age. The Crown is all metal, reasonably light, and my favorite. The Busch comes in as a close second, but the lenses available aren't quite as good as the 105/3.7 Ektra on the Crown. Most lenses for the 2x3's are at least good, many are excellent, considering vintage. Mostly the same applies to the 4x5, so its a matter of wanting the larger negative size available.
Jump in, I think you'll have a good time.
Harry