To me it's like the voice gets beamed into my head, bypassing my ears. I don't "hear" it, it doesn't "sound" like anything but the words are there. It can pronounce things different or with accents but it isn't a real voice.

I can only internally see the contours of objects if I don't focus on them. My inner monologue is my own voice unless I have been with my friends some time, then my inner monologue mimics their voices

Same here. I'm not aware of a term for it, but I've always been a bit self-conscious about the fact that I don't know what my inner monologue sounds like. I've tried giving it a voice, and it never sticks.

Some people don't have an inner monologue at all, actually !

Dunno what either of those things are called