I do not visualize words in the sense that I habitually connect them with a visual image. For me, a word i an abstract object in my head which is the word itself, not the thing it describes, or the way it's spelled or pronounced. From that word, I can summon things like the way it's spelt or pronounced, would I need that, but that takes some extra effort, so I only do it if I need to write or say the word, not if I'm just thinking it.
It's hard to explain for someone who doesn't think the same way as I do, but if you do, you'll probably know what I mean.
Because of this, sometimes things I say spontaneously are nonsensical because I say something else than I thought of. (This usually doesn't happen when I write though.) So I tend to keep a little "buffer" of words between my brain and my mouth to avoid missayings.
What I usually do as well, is think about the etymology of words, and sort of "taste" the words and see what they really mean by investigating and analyzing their (presumed) history. I think this is something NT's (And possible even people in general) don't do, they just learn words, and then take them for granted, so to speak.