and I’m super unclear what seeing things in your mind is supposed to be like.

It's hard to describe, but it's not replacing your eyesight. If I close my eyes I see black, or if there's some bright light I see red. But, it's like there's another visual channel going into your brain other than the one from your eyes. Most of the time, that channel is either off, or it's drowned out by the actual visual information which is so much more dominant. But, if your eyes are closed the fact there's no real information coming on the "real" visual channel means you're able to notice what the "virtual" visual channel is showing.

It's sometimes described as your "mind's eye", but for me, at least, it's not really like another eye because it's not detailed enough for that, but it's still as if there's an additional visual stream of information that goes from my memory to the visual processing part of my brain. For me, it's blurry and lacking in detail. It would be like using a slightly out of focus projector on a white wall in a well lit room. There are shapes and colours there, but they're hard to see. But, like an image from an out-of-focus projector, if you try harder you can make out more of what it's showing, and if you reduce other visual stimulus (like turn off the lights) you can notice more.

So for the ball example, I’d know the ball is “small, about the size of a plum, solid pink somewhere between neon and intense salmon, smooth matte texture, looks like it might be foam”.

Does this happen instantaneously for you? If I tried to come up with a description like that it would take several seconds, whether I'm doing it while actually actively looking at the object, or with my eyes closed working based on a memory of the image my eyes saw.

If you close your eyes and intentionally picture something other than the ball

Something real, or something I'm inventing with my imagination?

would you then be unable to tell me what color it was in your example?

Like, translate the image to a word? I can tell you a word, but the metal image will come first. I think I do need the visual representation to know the object. Like, if someone gives me a description of something, I'll build a mental image based on that description. If someone asked me to describe it later, I'd probably use different words because I'd be going based on the image not on remembering the words.

In your case, if you have a memory of something that is "small, about the size of a plum, solid pink somewhere between neon and intense salmon, smooth matte texture, looks like it might be foam", how easy is it for you to change the words you'd use to describe it? Like, say someone asked you to describe it but not to use any words related to living things, could you swap out "plum" and "salmon" without effort? Do you think you're storing those actual words, or are you storing a concept? For example, if you're remembering a white rock, is it "rock" you're remembering, or is it the concept of a rock, which can match similar words like "pebble", "stone", etc.?

Also, I wonder how this affects your ability to remember descriptions of things that are not physically possible in our 3d world, like a Klein bottle or a hypercube. I wonder if, for you, there's no real difference in difficulty remembering the details of a cube vs. a hypercube because you can't picture either of them. Whereas for me, I can easily remember / picture a cube, but for a hypercube it's hard because it's not something I can get a real visual representation of.