I am not sure any more how RM worked as stagebox in a direct connection, but it should be as it is in a network situation: A RM used as stagebox mirrors SL's outputs (main left + right, mono, auxes 1-14 and subgroup 1+2). The SL boards have no equalizer at all for their mono output, which is a sum of the main l/r mix with its processing included (PEQ, GEQ and dynamics).
A RM used as mixer allows the individual routing of channels to stereo main mix or mono main mix (or both at the same time). "Main" and "Mono" have parametric equalizer, graphic equalizer, compressor, limiter and fader. "Mono" (also called "center bus") additionally has a lowpass filter from 20 kHz down to 100 Hz, which is helpful for feeding bass subs.
The relevant quotes from the product descriptions:
* Stereo main bus with ... Mono sum XLR output
* 15 graphic EQs (for the first 12 aux buses plus the Main left, right, and mono/center buses)
* Variable lowpass filter on the mono/center bus
Hope this helps.