50-50% I'd vote for a 6x6. That way no issue with flipping the camera and possibly losing what you may want. As a starter, rather than a Yashicamat, I'd suggest the Rolleiflex T series. Between the Rolleiflex and Rolleicord in placement, basically a 'flex without the threading mechanism. 1st class lens, light and robust. It uses a coupled E-V shutter that can be used as such or the shutter and aperature set separately. Mine has a removable finder so you could put on the Porrofinder if you want. A huge lineup of accessories based on Bay I that are very reasonably priced.
I also agree with the Bronica ETRS series, my main system if you need the versatility but, as I am getting older, the T is making more sense and I am finding it does everything the ETRS can do in general shooting except change lenses but, years ago I learned to use my feet rather than have a bag of lenses. The Bronica for me is one of the best system cameras in concept and execution. A real workhorse as so many wedding photographers discovered.