"we" and other first-person-plurals

Typically “you” if it’s in my head, but if said out loud it’s “I”

Both. And often also by name for some sarcasms.

Depends on if I'm mad at myself...

"I should go get some food."

"You fucking idiot."

Depends which part of myself I'm talking to. If it's just a general conversation, it's "we." If it's more of a direct conversation to a part of my mind, it's "you." If I'm talking about myself to a third-party, such as this response, it's "I."

It took me a moment to realise this was about inner monologues.

Both, but it also depends on if I’m winning the argument or they are.

If it's my internal monologue it's usually "I"

If I'm writing about myself (like a journal) then also "I"

If it's a note to remind myself of something then "you"

I have written letters to myself in the future and those are always "you"

'One'

In my languages we don't usually use pronouns because verbs conjugations make them redundant, but I use both first and second person.

Both, with a slight preference for "I".

I think I mix them interchangeably. Much to the chagrin of my English teachers.

I am an "I".

I use I unless I'm insulting or denigrating myself, then it's usually you

I tend to just leave them out all together. Don’t know why though, maybe it’s faster?
It feels a bit like when you read a book fast and skip over entire words.

“Need to do some cleaning.”
“How could this be done faster?”
Or a common one:
“Hungry” :)

"I" or "we" in English, German is mostly reserved for deep thoughts where I rarely need to address myself but if I do I think I use "ich" ("I") as well. "You" wouldn't feel right for me personally.

I, we, you, they, kinda all of them. I kinda make up characters in my head and assign them positions and personalities based on the need of the moment, and address them as appropriate. I don't give them names or anything, it's more like 'that dick who keeps telling me to get off my ass and be productive can piss off', etc.

Interesting that several people are reporting using "you" for negative sentiments, because I use "I" for those as well. E.G. "Well, I'm a fucking idiot."

I, you, we and thou.

As in:

"What am I doing?!"

"You're getting older, not younger."

"Let's not do this again."

"Thou have lost the little bit of reasoning you had left."

And it scares people.