For new standards, yes. But ASN.1 was first specified in the '80s, and backwards compatibility is a thing. So really it depends on what you're doing: if you can start with a subset of ASN.1, which I think is done in MDER[0] and OER[1], you have a bit more freedom. But if you're working in legacy formats and standards that operate internationally, you could run into problems.
Kerberos implementations generally just-send-whatever in IA5String fields. That means Windows sends UTF-8, and MIT Kerberos and Heimdal send whatever the user's locale uses. Windows doesn't normalize or anything. It works in that a) it interops when using ASCII names, b) it interops when using non-ASCII names in UTF-8 locales on Unix. It violates the spec, but it works.
The 90s were rough on text encoding, but it seems pretty settled now.