Hahahaha, I guess it must be pretty wild to hear about for the first time! I felt the same way when I was shocked and envious people could just like, picture what their loved ones looked like, though I was soothed by the fact not as many people can easily conjure their loved ones’ voices up. My knack for voices also makes it quite a lot easier for me to detect how someone’s feeling- there’s a lot a voice gives away, and people usually care more about controlling their facial features or body language.
I imagine it varies among people who have it, and how uh, much, they have it, hahah. But for me, fantasies tend to be more along the lines of a sensation of touch, (which I can also conjure up quite accurately on command) and voices. My daydreaming is mostly just me closing my eyes, and seeing the pitch black (or slightly ‘glowy’ red of light entering through my eyelids, and the little sparkles of colour you get from mushing your eyes shut too hard for too long or rubbing them) while letting myself get carried away on some sensory scraps (a sensation of warmth, like slipping into a bath, is usually a common backdrop) and thinking about either someone’s voice, or like, if I’m fantasizing about eating a delicious treat later, the phantom taste of it- not enough to really satiate, but to whet the appetite and make your mouth water. My other ‘fake senses’ (because you’re not really hearing someone speak, you know it’s just something you’re thinking of) are quite strong, maybe because I can’t visualize stuff well, so it compensates?
I actually use journalling as my main method to outline having a difficult conversation- I find organizing my thoughts in text quite helpful, as often there’s a lot of vague sensations in lieu of clearcut pictures- rather than imagining a lovely beachfront, I could ‘smell’ the salt in the air, ‘feel’ the rasp of sand on my feet, ‘hear’ the crash of waves, but no sight of bright blue marinas anywhere in my head. So writing them out helps. Sometimes, if I’m trying to think of how the other person might respond, I might ‘hear’ it in their voice, which can be quite distressing hahahaha. I am very prone to rumination, (hence the diary) and so yes, I can get caught up on snarled lines of thought.
EDIT to add: I think the thing I am singularly most envious of, is being able to just… imagine what your loved ones look like. It’s a huge part of why I take so many photos at any opportunity, because it’s so comforting to be able to see what someone you cherish looks like- how they smile, the crinkle of their eyes at the corners, a glimpse of teeth. I also write a lot of poetry about the people I love, usually while studying one of those photographs- and try to capture their tiny little details as well as I can, as a way to preserve them, in a sense. The soft dappling of sun-kissed freckles you have to lean in close enough to kiss them to see, the beauty marks stark against her face under a cascade of fluffy curls, the little crinkles at the corner of his eyes that show up most when he’s smiling alongside the start of crowsfeet…
Hands are especially evocative to me- the shape of someone’s nails- if they keep them long and tapered, square and blunted, the veins on the back of their hands, the notch and ridge of knuckles and the soft skin in between, scars and blemishes and callouses, the bump of a writer’s callous- they’re so full of lush details to linger over and write about. I might not be able to see them on command so to speak, but to hold someone’s hand and study it, before cataloging it best you can in a little love poem: that’s a really lovely treat.