This is enlightening. I had so many thoughts on this, so I started this reply as I read through other replies.
When I was younger, I thought in pictures. I had trouble communicating, because I would see the picture, then try to describe it in words. But I would see 100 pictures per second, so my words would always fall behind, and I would even forget what I was saying, because I was concentrating on the pictures. Written communication has always been better for me (even though I'm not a great speller). I always felt I was different in this regard.
I'm not exactly sure when the change happened, maybe it was in high school or maybe it was after my car wreck shortly after I graduated (no signs of head injury), but now I don't really think in pictures anymore. I still sort of have the pictures, but I process them subconsciously, and think more about the ideas. Still no words, but these translate better to words. Although, I feel like it's a slower process, although maybe some of that has to do with aging.
When I was young, given a math problem, I would just "see" the answer. I would have troubles explaining why it was correct. I learned algebra when I was 6 or so. When I actually took the course, I struggled a lot, because even though I had the correct answer, I had troubles showing my work. When I learned to do this, I feel like my brain was rewired, and I could no longer just see the answer, but I could follow the path to the answer, which takes a lot longer. So maybe this started the change with the pictures.
So, I naturally think visually, but I totally understand aphantasia. If you say think of the beach, I might think of sand + salt water + sun + the concept of ocean smell (I don't actually smell it) + sea shells + hammock. I add them one at a time to a concept, but not really an image. The longer I think about it, the more details I add. After a point, if I have a specific memory of a beach, I might pull that out, but it's not something that comes quickly, it might take a few minutes to get to that point. With the beach example, I lived by a beach for two years, less than two years ago, so to say it takes minutes, it seems like eternity, and I usually don't make it there unless I'm alone. Similarly if I think of my mom. I might feel love, but to see her takes time. And it's usually in black and white, or really black and red, you know, what you see when you close your eyes.
When reading, I do see things, not like a movie, more like how I think with flashes of images. I can create an image for someone, but it usually has nothing to do with how the author described that person. I only saw the first Harry Potter before reading the books. So while I had images for some of the characters, I completely created the others. Ginny looked nothing like the movie Ginny, although Umbridge was pretty close. But Rowling was pretty brief in her descriptions, and I liked that. I attempted and failed at reading Lord of the Rings, because of all the details. I never could put them together to create something. Actions and talking are important to me when reading.
I have no inner monologue. I always thought that concept in TV shows was genius! Evidently that's just how most people think. I do sometimes have music going on in my head. I can "speak" in my head.
And for the fluid vs crystal intelligence, mine is super fluid. I'm an engineer, and in college, as a professor would start deriving a proof, I would finish before he would, sometimes dozens of steps ahead. I was very very good at those types of image problems.
Emotions are also a problem for me.
The "I don't know" and the "what are you thinking about - nothing" are definitely me.
I have troubles extrapolating what people look like. Like if I haven't seen a friend since high school, it is likely I won't recognize them. And if I've met you once, I won't remember your name at all, no matter how many times I said it in my head trying to remember it. I'm pretty good at "I know you somehow..."
I know facts about my past, but I have few memories going back more than a few years.
I'm great at directions. I usually have to orient North once at a new location (like if I've driven a hundred miles), but otherwise, it takes me a second to figure out where North is. But I'm horrible at distances. I can get the order of magnitude down, but is that car 100 feet in front of me or 500 feet? I really have no idea.