Back in the day when I was thinking about this I kind of thought of myself as pre-visual. I'm sure I have multiple modes of thought though, and I'm also sure this is true of pretty much everyone.
I've had way too many instances of not being able to find a word to express an idea, or not remembering the specific words people expressed but just what I think was the gist of what they said (whether or not I interpreted them correctly) to think of myself as a verbal thinker. When it comes to word production sometimes they just come, at other times it takes me time, and I can go into a state where they just flow, but in that state my conscious is checked out of the process. It has the experience of an autonomic process almost.
I do have an inner monologue though (frequently caught up with OCD counting, or at the moment Taylor Swift's Anti-Hero song as well as speaking the words I am writing as I am writing them).
> only an idea pops up in my head without any specific image and I have to try really hard and describe the horse with words to make some kind of misty parts of the horse
Is this idea the words which describe the horse, or a pre-visual/pre-verbal idea of a horse?