i think the gary stu/mary sue thing can be hard to judge without being able to evaluate how op a character is in comparison to the conflict of the story. obvi rules are different for rp, but for fiction i’ve found that worrying about it sets me back. like there are a lot of films, books etc that have what would be very ‘mary sue’ characters (thinking of james bond rn lmao) but as long as the conflict actually challenges them and forces growth, i think one can be more lenient on themselves about being op.
if i had to choose an example from my ocs, it’d be dahlia - she’s a very skilled secret agent, and part of the top squadron of her agency (and is relatively young; 27). then again, given that the plot is about her not being able to rely on the agency or her skills, she’s challenged anyway and it presents a decent conflict.