Answering your second question first...
Originally Posted by slnce-z-gsi
Based on the manuals you can download from the Mamiya site, it looks like a fully equipped Pro Tl (back, pentaprism, 80mm f/2.8 lens and winder) at about 4 pounds weighs about 75g more than an AFDII without lens.
As to your 1st question...
It might help to have some context - my 35mm stuff is small (Olympus OM, without winder, and prime lenses only, mainly). Despite that, I have no problem with a Mamiya 645 Pro. I don't often use a power winder, but I do use a left-hand grip and a focus assist lever.
Some further context might also help. For decades I've used Mamiya TLRs handheld, including doing wedding work. In recent times, I've been experimenting handheld work with even bigger cameras - a Mamiya RB67 and a Koni-Omega rangefinder.
And finally, more context still. Essentially I use my cameras with 1 1/2 hands, as I have limited strength and dexterity in my right hand.
IMHO, the weight of these cameras is far less important than their ergonomics.
Hope this helps. Don't hesitate to ask further questions.