I never really thought of it, but I sort of have a mixture of verbal (internal) and visual. But I'm mostly visual/non-verbal in thoughts, unless I'm trying to figure out what I should say or type..
It is all mental strength, but visualizing things such as.. distance from an object is easy when I'm in the car. I'm very poor at it [judging the distance of my body to an object] unless I'm 'calculating' the possible point of contact between to objects [that are not me and an object] or how things work (like gears, or even things like circuitry..). I like pick up a lot on patterns, someone's gait being smooth gets me studying. Cars rolling by slowly gets me the same way, but I have an affinity for vehicles. I try to predict what one action will cause another reaction, but it doesn't always go over smoothly as I can't control other people obviously. It's all very visual.
Describing thinking style is difficult when you have no idea what to use as descriptors, but I have an exceedingly hard time with verbal questions. If you ask me something beyond what I'm trained to hear (like things at the job, mostly 'what is the price of this'), you'd be lucky I would understand it without having to pause, process it, and reply about thirty seconds too late (or more). I'm very poor at my verbal calculations.. Word problems (especially in math, I probably failed algebra and geometry due to them) always gave me issues, it was like getting internally confused. You're trying to visualize the objects presented in a word problem, but then they're telling you to attach this explanation or numbers to figure out the cause and affect? It doesn't work that way for me.
I might do math out on paper to calm myself, I write all my finances down and stuff.. but if I can't physically show you by drawing what I mean.. well, I'm certainly not going to be able to verbally explain it.