I don't know how well and how fast could the telepaths use each other's memory, or habits, or mental associations, or things like this.

Sure. To the degree that I assume that telepathy does not successfully bridge the distance between minds, such that between-mind operations remain less efficient than within-mind operations, then I agree with you... in that case, a telepathic society is more like the real world, where minds are separate from one another, and the between/within mind distinction matters more.

But (for me) the important issue is the degree of internode connectivity. Whether those nodes are in one mind or two is merely an engineering detail.

traits like "learns a lot about X" and "spends a lot of time doing X" give better output if they happen to be the traits of the same person (as opposed to one person who learns a lot but does nothing, and another person who does it a lot but doesn't understand it).

Similarly to the above, I agree completely that they give better output if they are tightly linked than if they are loosely linked or not linked at all. I would say that whether this tight linkage occurs within one person or not doesn't matter, though. Again, in the real world we can't separate them, because tight linkage between two people is not possible (I can't use your knowledge to do things), and if telepathy doesn't help us do this then we also can't separate them in the OP's hypothetical.