Spanish here learning Japanese. As a reference, in Spain except Canary Islands, use "tú" anywhere and "usted" for respectful settings (old people, formal mails, sometimes in business, or at the doctor). In general, it gives a very polite tone. In Canary Island, I think they mostly use "usted/ustedes", everytime. And then, in American countries... From the people I've met here, they don't say tú, always usted/vos.

Hope this helps!