I have a Yashica, Minolta Autocord and a Rolleiflex tlr. For starting out, I think you should consider getting a Yashica, unless you can get lucky and get one of the others for a good price. Try to get one of the earlier Yashicas with the Yashinon lens. The later Yashica 124Gs are nice but they are over-priced in my opinion. See if you can get a deal on an early Yashica 124, Yashica D, LM, etc.
Ricoh made some very nice tlrs as well.
If you get a Yashica, consider flocking the film box to reduce flaring. One some models the film box does not absorb light properly leading to annoying flare. Flocking is quite easy to do.
I have a Yashica 24 like johnielvis and also have had no problems in terms of sharpness using 120 in a camera that is supposed to use only 220.