The boundary is certainly Sorites-fuzzy, not much can be done about that, I suspect.

people disagree about the direction of motion there?

I did not mean that, no, but who knows.

A person controlled by Borg implants seems like a good example of 1, but I think you'd find widespread agreement about what changes would make that person more or less free (except among those who insist the boundary is sharp and binary).

I tend to agree, but I can imagine a counterargument "but this person can still imagine other choices, and would follow them if not for the implants". By the way, no need to go sci-fi, just replace Borg implants with voices in your head, or being physically restrained, etc.

As I said in my other replies, I don't imagine how the issue of free will can be productively discussed without people agreeing on hat they mean by it in non-central cases.