Style is a manner of address, an honorific that comes with a noble title. For example, HM Elizabeth II is addressed "Your Majesty".
In a fantasy setting that does not pretend to be Europe, I have chosen noble titles that are not "King", "Duke", "Earl", etc., but "Shah", "Vaspahr", "Sardar", etc.
Now I'm trying to understand, is it right for a Vaspahr to be addressed "Most Noble" and "Your Grace", or are those reserved to a British duke? Would those forms of address sound out of place when used with a non-European title, or are they standard?