I have the Pro so I have interchangeable backs. I've never handled one of the earlier ones.
It is certainly bigger and heavier than any of my 35mm cameras, and also than my Yashicamat 124. But compared to most 6x6 or any 6x7 camera it isn't. It's very hand holdable but you won't forget you have something around your neck.
I totally disagree with the suggestion of losing the prism for the WLF. WLFs work best for square formats, or cameras like the RB/RZ 67 with rotating backs. For a non-rotating back rectangular format they are not very useful, make it almost impossible to shoot in portrait orientation.
I don't have, nor have I used, one of the left hand grips. I have the winder grip, which is a right hand grip. The camera handles great with it, even if it is a bit big and heavy. I never noticed any problem or oddity at all with focusing the 80mm lens or any of my others. The only odd thing to me is that the aperture rings rotate backwards compared to all my 35mm lenses so going back and forth can be confusing. I also wish it showed the aperture in the viewfinder which both my LX and MX do. But those are minor quibbles.