I have no internal monologue. No voice in my head and also no words. I can't even imagine what my voice sounds like (or my wife's voice) unless I hear it. And I also have aphantasia. It's totally silent and totally dark in my head. (And when I'm typing this, I know the ideas I want to communicate, but I have no idea what words I'll use until I see them on the screen.)

As far as I can tell, I think in abstract ideas.