Should I turn on two-factor authentication for my domain registrar account?

Yes - and it is one of the highest-value security steps you can take, because the registrar account controls your entire domain, including where your website and email point. Without it, a single stolen password is enough to take the lot:

• Why this account above others - whoever holds it can repoint your site and mail and lock you out, so it deserves stronger protection than an ordinary login.
• Use an app, not SMS where possible - an authenticator app or security key is harder to intercept than a text-message code, though any second factor beats none.
• Cover the email too - password resets land in your inbox, so the email account behind the registrar login needs two-factor authentication just as much.

Turn it on at the registrar and on the email account behind it - together they are the lock on your whole online presence.