Everyone is different, I have random days where I won't be able to interact much between my alters but most days I'm at least able to hear them half the time. It used to be less. We have a hard time with headspace visualization but our partner doesn't.

we struggle to see *anything* in our head, but over time we have gotten better at interacting with each other in the headspace. for a long time, it was literally just fog when we tried to "look inward"; thick and heavy and it muffled voices of others. over time we could pull people out of it more, especially when co conscious. we're better at mentally visualizing with other senses, like "feeling" the touch of other alters, and we can "feel" where our bodies are and how they're moving in the headspace and how we physically "feel" in our head, so we try to picture ourselves using that information and ground with it at times. if any of that manages to make sense! we can, at times, "see" a couch in the headspace as well, and music can play from a radio that we have a pretty good mental image of, but we don't have a full "inner world" like many others do, just kind of a "front space" that we can access. but, in answer to your question, it is broad, and it is by no means a stagnant skill. visualization in the headspace or of inner worlds can change system to system, and can change on a daily basis within a system! and it's a skill that is usually guided in therapy and can 100% be improved and built upon! currently, we're trying to make a "safe space" of sorts in our head, but we're struggling to keep it tangible and safe-feeling. we've been having some luck with resources on kinhost.org . there's a LOT on there about not only internal landscapes and inner worlds and meeting places, but also improving communication in general.