The precise powers of the Emperor vs the constituent Monarchs is...Unclear as of yet. (Fairly) definitive powers at this point are:
1. Control of X% of each realm's income, where X is their ranking, delivered each winter (going to try and make winter the party/tournament/RP season).
2. Right to set campaign seasons.
3. Right to influence diplomacy if there is a major benefit to the empire as a whole.
4. Right to disallow religions/guilds/nobles throughout the empire (though /not/ to force acceptance).
5. Right to all communications upon request.
Some of that is, of course, vague. We may leave it that way, though I'm not sure yet.
Common external diplomacy will sometimes fall into point 3, but again that should be a power used sparingly if ever. Emperor will have no direct powers over the legitimacy over member Rulers (though informally having the Emperor as your enemy would make life quite difficult).
