For me there’s two separate participants, a ‘talker’ and a ‘listener’. My mind identifies more with the talker, because that’s the one that has agency. Since there are two participants, both of which are me, I talk in 1st person plural (‘we’ve got to do …’, 'we thought about this earlier’). I stopped being afraid of being alone after I started having an internal dialogue around the age of 11, since having a second participant in the conversation meant I was always in company.
My internal monologue is constant. Unless I’m using my language processing capacity for something else (e.g. listening to a podcast or reading text) then my brain is full of verbal diarrhoea. I’ll count each step on my way up a staircase just to fill the dead air in my head.