What a single O5 personal can and can't do?
they are obviously allowed to read anything they want. (well, unless its memetic)
This is something in the field of headcanon and is up to you.
I personally believe they work like a congress or some other kind of committee, voting on procedures and projects that affect the entire Foundation. However, each member of O5 command has a field of knowledge and responsibilities in which they can exercise unilateral control, provided they inform the others after doing so.
I always imagined them as a committee that gathers in an underground bunker behind sealed doors to discuss matters important to the Foundation.