Do titles actually have any legal standing? I use Ms where possible, but get correspondence addressed Ms, Mrs and Miss, even from official sources.
Not in the UK they don't ilkley. You can call yourself any of them regardless of your marital status. However, I suspect OP is going abroad, and the rules may be different there. I'd check first if I were her. There are no titles on passports but there are on tickets sometimes.
Also, changing your surname to your husband's when you get married is intrinsically anti-feminist because it's following a patriarchal custom. Whatever your reasons. Even if you hate your father, there was nothing stopping you from changing to your mother's name or something else that didn't relate to him, before you get married. Call yourself anything and everything you want, it's a free country, but don't pretend something is feminist when it's the exact opposite. And no, this isn't about anyone being a better feminist than anyone else either: we all live in a patriarchal society and we're all influenced by it every day. It's just about not deluding yourself that because you want to do something and you're a woman, that means it must be feminist. You can still be a feminist whilst doing some anti-feminist things. Otherwise there'd be no feminists at all.
Lastly, 'it's just a word' is a piss poor argument. There are quite a lot of things that are just words that we would all, I hope, not use and understand why we shouldn't use them.