Please read this version and discard the prior one there are some typos in the prior version:
No difference except you have less time in CC for a beat (approx.: half a second) than in CC. The walk is normally considered a full beat, as opposed to the step which is normally a half beat, and the entire look of motion should be different than the walk. (There are teaching videos on this.)
The foot speed is the same in forward walk (in CC and R) your foot (not your body) arrives on the floor on the beat. On backward walk you put down your heel on the beat (full body weight not yet transferred).
In my humble opinion, in the walk the difference is only that that the dancer has more time in R, therefore more expressive upper-body and hip-action, also in the speed of transferring body weight. Especially on the two-beat slow of R. I dont see any difference in the foot-speed. However, caution must be taken not to confuse the walk with the half-beat step in CC, as I noted in my prior post. That is a totally different motion non-existent in R.
This is a very interesting topic. Teachers and advanced dancers lets hear your opinions, please.
RE: . There can be a big misunderstanding here. To be technically correct on a Forward Walk in the Rumba the heel should be on the floor on the beat which means the inside edge of toe must be fractionally ahead of the beat. This also applies to the Samba. Heel on the floor on the beat otherwise you will be chasing the music I agree. No misunderstanding. I think I was saying that in a different way. I think most people do it more or less correctly on the Forward R Walk, but there is a diversion on the Back-Walk.
With regard to There is no closing of the distance between a couple dancing the International Style Rumba, I am not sure if I agree. For example on the one hand connection a forward Basic on the 2 the Lady stretches away and she closes on the 4. Similarly with the Fan.
RE: Its good to hear some sensible questions being asked. Yes, a good discussion is very helpful, and so is hearing other dancers opinions and experiences.