When people incarnate as a walk-in, do they indeed inherit the prior soul’s karma, because their new body is still attached to the akashic records of the prior soul’s journeys in the physical plane?

In a broad sense, this is correct because the DNA and soul configuration of the body will have come from the prior owner, and their connection to the akashic records will persist for things involving that physical level of the bodily workings, energetically. And because it is linked to them as a soul-based being, many things that can ultimately influence the course of one's life might be projected from the soul of that prior occupant, and certainly from the akashic records, with the Law of Karma seeking to rebalance things. That will continue to happen, even though that person's spirit is going back to the light and the newer spirit taking up residence. So this is simply a kind of housekeeping the new arriving walk-in soul must contend with. But typically, their own karma will be different enough that this will not represent a compounding of difficulty, giving them too heavy a headwind to advance successfully, following their arrival. In many cases, helping to heal the prior karma will be relatively straightforward because it will not be something too difficult or overwhelming, being someone else's business, in a sense, and thus less complicated to unravel and rebalance. It still may take considerable time, and may remain a work in progress for the balance of the lifetime. But this is a trade-off in taking a shortcut to come in later in life than as an infant, so as to get right down to the work needed, or the life mission.