G is the last camera I would call as rangefinder. It is auto camera.
With overpriced lenses and way too much of electronics.
R is true rangefinder. Has TTL metering, which is handy and using very easy to get batteries. And you will safe a lot on lenses. It works with FSU 50mm lenses. They are 9-50$, will do great for BW. And R will accept less expensive than M-mount LTM lenses. Color Skopar 35 LTM is possible to find for 250 USD and it is small, modern lens. Or old Canon LTM 35 lenses for same price.
FSU is very big gamble these days. Where is maybe one USA based seller, who stands for what he sells. The rest are mostly scammers on eBay from FSU countries. In 2017 I purchased, FED-3 and FED-5B. Both were listed as serviced and tested. But they were not. I have money returned for FED-3, but I can't fix it, yet. FED-5B was just fresh enough to still works without CLA.
Where are Canon P all metal RF cameras. Build long time ago, but still works. Not expensive are available.
If you are Nikon guy, then were are Nikon RF cameras. Some old, but still working fine and where are some made as replica of old ones, but working as good as old ones.
Old ones are not very expensive, but they are at their own league. I don't know who is servicing G, but Nikon RF cameras are still serviced within USA and sold after service.
You could also get serviced LTM Leica for very reasonable price and it will works with mentioned above FSU LTM lenses. Best match would be Industar-22, Industar-50 they are collapsible and will not block viewfinder.
If any other lens used, it needs external viewfinder. They are expensive, or DIY, or buy FSU universal one (not expensive).