Naming concerns as Foreigner

Hello, I’ve done a little sluething in this subreddit and have gotten kind of vague answers for what I need. So I decided to make my own post.

I am half japanese half american, born in america. So I am a foreigner, but my name is japanese (Kota). I’m not sure how naming applies to me? Must I write it in Katakana because I am foreign born?
From the research I have done, people who are chinese have to do katakana as well? But I haven’t seen anyone with this issue.

I do like the kanji spellings I have seen online (although I don’t know which is the “correct” one, I don’t even know how to figure that part out?)

So TLDR: My question is, how do I know whether my official documentation needs to be in Kanji, Katakana or Hirigana? Is it up to me? If I were to chose a Kanji spelling, would that impact me in any way (legally, socially, ext) does it also matter whether my last name is japanese or not ? (It is not).

Thank you so much!