WLF for later model mamiya 645 (Super, Pro, Pro-TL) are very hard to find and when found, pretty expensive. Good luck on finding one and at a price that's affordable. AE prism N (one originally made for Super) is reasonably priced and that's what I use with my Pro.
Having a motor winder makes it more like 35mm bodies in terms of ergonomics but it makes the whole kit much heavier. I tend to use mine with hand-crank more often.
Don't forget to get a strap with Mamiya clips. These cameras require a special clip that attach to the knobs on the body.
I have a 80mm f/2.8N. I'm not sure if I would spring on f/1.9.... I never felt a need for one.