I prefer Oxana spelling but I find it a very beautiful name. I think of Oxana Fedorova, the dethroned Miss Universe. She is very problematic as a person but when she was in her prime she was very beautiful. Slavic women are unmatched beauties. So when I hear Oksana / Oxana I think of a very captivating and unique looking woman with pretty eyes. It also sounds like Roxana, the wife of Alexander the Great.
Mykola sounds like a type of bacteria. I don’t have any other associations of this.