I handled a GS645 recently from a fellow camera club member, was surprised about its lightweightness and the haptics were fine. The owner recognised that it was a delicate camera and the RF appeared slow.
"Texas Leica" GW690 owner for 10 years here, no issues. Paraphrasing someone out on the net, the 645 series do not share that Spartan reliability of the 6x9. Side topic that the AF cameras, despite some electronics, have a Shop in Poland that can replace some flex cable issues. Not economic as well, but fixable.
I originally bought Fuji 645 folder for negative larger than 35mm, while easy to carry around. Disappointed with its quality of construction and rather bulky size. My Super Ikonta A is very small by comparison. Also more robust construction. A post-war Super Ikonta B (6x6) is also a good choice for a folder.
Of course, camera choice is very personal. Also depends upon one’s subject matter. That’s why so many varieties of cameras were produced.
Good luck!
I went that way, with a Super Ikonta IV. Some age hiccups but these are compact and reliable. However, there are some shotcomings such as no framelines, the Tessar has a much more vintage rendering (Spoiled myself with the Fujinons) and it's a 6x6. The Super Ikonta A seems interesting and wouldn't say no to one falling into my lap to adopt, but also never updated to an integrated VF-RF.