The part about accents sounds interesting to me. I always believed I can't do accents because I absolutely can't fake/hear them in my head. I can even only speak my own accent with close family and switch to regular German with everyone else. I also can't hear/recall music from memory, so it's near impossible for me to sing freely, while singing along works fine.

I can imitate different voices in my head when reading a novel and I can't even comprehend how one would read and comprehend without hearing everything spoken in ones head. It's just impossible for me.

I do have a constant monologue though that is impossible to shut up. Even if I try to calm it or meditate I would think out loud "calm/meditate/don't think", so that doesn't work at all xD

I did start thinking in English at some point. Before that I would translate all English to German, think about it and translate my German thoughts to English, if I needed to say something. By now I just think in English when I'm in an English context. It feels entirely natural.