CRM addresses the social aspects of crew interaction; it does not
address the technical aspects.

I am not an airline pilot, and I don't know the "technical aspects". I
also have not taken a formal CRM course (although I am familiar with CRM
from FAA safety seminars). So, take my words with as much sodium
chloride as you deem appropriate.

I suspect that the answer to your question as to who does what is to
some extent dependent on each individual crew combination. And if an
airliner is on autopilot most of the time, nobody is "holding the yoke".
I understand that the captain, the PIC, the one in charge, can allow
(say) the first officer to hand-fly an approach, or do it himself.

CRM came about because in the past, sometimes the PIC was "too much" in
command, intimidating the rest of the flight crew in such a manner that
they would fear to question inappropriate decisions made by the captain.
CRM is an official recognition, and enforcement (of sorts), of the
idea that two heads are better than one, especially when one is swelled
up. It fostered co-operation rather than subjugation. It deals with
authority (among other things), and requires crew members to give
appropriate input, and to listen to and consider that input.

CRM is an important consideration in =deciding= who does what, and when
(and whether) somebody else ought to. But as you say, it does not by
itself assign cockpit duties.

Sometimes I fly (real spam cans) with another pilot. In that case, I
have on occasion delegated radio work to that other pilot, but I find
that I prefer to handle it all myself, for a number of reasons. First,
I don't fly all that much, so it keeps me sharp to do all the tasks
myself, since I sometimes fly by myself. Second, I don't fly with a
crew all that much, so I find that if the other pilot is doing
something, I may not be aware of it to the same degree as if I did it
myself. And third, most of my flying is "easy" flying - small aircraft
requring only one pilot in fairly benign conditions. Larger aircraft
require two pilots becuase there is more to do.

Alas, I don't really know what it all is.

Jose