It's critical you purchase a camera (tool) appropriate to shoot subjects your interested in.

- you excluded sport and bird photography.
- you like a Olympus XA and don't care for bulky cameras
- want a M6 except for cost
- had issue with slow slow lenses (there go most light RF cameras)

Suggestions

- 6x7 Plaubel with 80mm f/2.8. But that camera is no less expensive than a Mamiya 6.
- GS 645 cheap, small, excellent lens
- Bronica RF 645 with 65m lens; less than a M6 and a better camera in smaller package
- Rollei TLR with f/2.8 optic; small, fast lens, slow shooter unless zone focused.
- get the M6 if you want it