I would say yes and no to that. Yes they view their role as serving the director's vision; no it is not an issue for them to impose their style on the film, particularly given that is usually the reason why a director chose them in the first place and continues to work with them in the future.
I agree.
No - particularly as regards your second point, Leone was fantastic at framing his shots and he quite clearly must have been working very closely with the DP when shooting all of his films.
I don't think he was. He was great at imagining them. He was great at structuring them. He had some great framing ideas (keep the chin out of the frame, frame the guy between these elements in the foreground........) but the execution in non Delli Colli films is poorly done. It's still good because Leone's ideas were great enough.
If you want me to rephrase in a way we'll probably agree: FOD, FFDM and DYS would probably have (much) better shots if Delli Colli had done the cinematography.
