re: 2:3 format - I wish I had a good answer for you. Have shot for many years with an M2, and loved it. Then moved to 6x6, with some affection for 4x5, and worked composition harder for a long time. Both of these are elegant proportions. Along these lines, 4:3 is acceptable, but the 2:3 less so. Theres something forced in 2:3, the long side is always driving the other side, and not necessarily gently either. Is this a subjective opinion? Absolutely, no doubt about it.
For some shots, its fine, and can even work nicely. But for compositional excellence, it just doesn't feel right. There. Said it, flames to begin.