I have a few Canon RFs, IIS2, L1, P, 7sz
I am quite fond of the IIS2, I think it's that model, 1/500 top speed, both X and FP sync, shutter with modern speed progression. I use it with the VF mag at the highest and a modern accessory viewfinder in the shoe. Focus with the magnified image, frame with the Aux. Using it that way, I might really like a Leica IIIg, but this is what I have. I love the solid feel of the bottom loader. Loading is a pain, but not too awful.
I could use the L1 the same way, and it would be fine. The copy I have is kind of beat up, but everything works just fine. Loading is easier, but the hinged back feels less solid than a bottom loader.
The P is very usable. Like many here, I don't think the 35mm frame is all that usable. Nothing wrong with it just less quirky than the older models. I've had some light leaks, but they're really easy to fix with some velcro loops in the two tiny spots near the back hinge.
7sZ, very likable. I think the meter works, but haven't tested it recently. My copy has a vertical alignment issue in the RF, otherwise it's very nice, and my copy is in very good condition.
I really don't think you can go wrong with any model from the IVSB2/IIF2/IID2/IIS2 on.