I prefer aphantasic, since it's an adjective. I'm okay with aphant, though the noun form sounds weird to me in a sentence (I am an aphant vs I am aphantasic). We generally only use nouns for things like profession (I am a writer, a student, etc) and use adjectives for personal descriptors (I am tall, short-sighted, Jewish). I think "person with aphantasia" is kinda clunky, but I wouldn't be upset by it. None of them are offensive or anything. Personally, I use whatever makes most sense grammatically. If I'm describing myself, I'll say "I am aphantasic." If we're talking about what life is like for us, I would say, "Living with aphantasia..." or "Having aphantasia..." Now, plurals are a different animal: aphantasics doesn't sound quite right, so I'd go with either aphantasic people or aphants. Interestingly, the awkwardness of "aphant" in the singular is not present in the plural; "aphants" sounds natural. I also feel like the plural "people with aphantasia" doesn't have the weirdness of "person with" so I'm actually fine with any of them in the plural. Most of the time, I'll go with identity-first because it makes more sense to me conceptually (I *am* this way), and that's also usually the most grammatically-appropriate form... but if a different form would work better, I'm not gonna twist a sentence into an awkward knot to try to force it to take a form that just doesn't fit. In some cases, you could tweak the sentence to use the other form, but in some cases the grammar really wants to go one way or the other, so I just let the sentence guide me.

We've been following the researchers lead when it comes to language. As you noted, researchers are largely using the term 'aphantasic' - including Zeman, Pearson, and many of their partners, who collectively make up a large majority of the extreme imagination research space. There actually is more disparity in the definitions of aphantasia then there is in the terminology used to describe a person with aphantasia lol