I have multi-layered thinking. There's images, there's an inner monologue, there's a constant earworm. There may be more than one string of each, I'm not sure. They're all there all the time, but one may be more foregrounded than others, depending on what I'm thinking about, and I can focus on just one line of thought when I need to. Mostly when I need to; if I am particularly worried about something, it will keep coming up to the top whatever.
I think in different ways for different things - a lot of it is words, but maths- type stuff is more images, though I think the inner monologue is still there, saying things like, "that's not balanced." The inner monologue has different voices, depending what I'm thinking about. I do try to shut it down when it's my mother, though, as that's usually negative, unless it's about gardening.
It's difficult to know how I really think - the mechanics of it, I mean - because thinking about how I think changes the thinking through being observed. I need to sort of creep up on thoughts from behind before they realise.
I like lieing in the bath and letting thoughts just drift around.