I am not sure I can say this any clearer. They do not keep the same secrets internally as externally. To the public they keep their cards close to their chest about upcoming developments (not necessarily more than anyone else). In actual production they limit script access to stifle spoilers. With Marvel Entertainment sure they are not constantly on the phone discussing script input because they don’t need that (although sometimes it might have been a good idea).
They will be required to consult with Marvel Entertainment over IP usage, marketing plans, publishing issues etc.
It would be in their mutual best interest to also discuss longer term strategy like where and how they plan to take characters and concepts. Because ultimately they don’t belong to Marvel studios.
So what this means is certain Marvel Entertainment board members will have regular updates on what is happening over in Marvel Studios. This information will inform the strategic choices of Marvel Comics. What that means is that certain concepts, themes, character choices and sundry small details will be provided to the relevant editors as and when it is appropriate. When an editor says “I had no idea what the plot of that movie was going to be” they are not lying, but they are not telling the whole truth. They probably knew quite a few elements, just not the plot details. Ultimately they don’t need to know the plots, it’s not as if they are going to commission a writer to write the same story as the comics.