Welcome to APUG.

I can only help you with mamiya 645. Mamiya Pro-TL is exactly the same as Pro except it won't do TTL flash. So, if you don't do TTL flash photography, you can get a Pro and save few dollars. Plus Pro models are more available. It's a fine camera. I liked them when I had those. I had a Super and a Pro.

It's not a light camera though.... I don't think rest of your 645 models are significantly lighter (if any) either. With a motor winder and a prism finder, it operates pretty much like a big 35mm camera. I just put up with the extra weight as payment for quality negatives. I hand held mine as well.

If weight is an issue, might you want to consider Fuji range finders like 645zi?

I went the other way around. For even bigger negative, I went to Mamiya RB-SD. I hand hold that too with a bracket!