RF is first and foremost a FF system, not APS-C.RF will be the bread and butter for canon even with some APS-C cameras: R7 and a 90D equivalent.
EF-S can be adapted of course, but they will likely to not start making crop sensor "RF-S" lenses.
EF-M is the way to go if one prefers to have smaller, cheaper lenses specifically designed for APS-C sensors. They are not going to start all over once again.
Nikon has been thinking the same way (they are not going to make premium APS-C lenses, only the smaller and cheaper ones like EF-M), except using the Z-mount for both systems.