If you follow this advice, you should pretty much be solid on Monarch:
Whip whenever you can, there are only 3 reasons not to whip:
1)You can't (Not enough pop, or it's lategame and you're out of slavery)
2)Your city has grown to a size where whipping isn't practical, ie it doesn't give good returns, usually when a city grows over pop 8
3)You need to spare the whip because happiness is an issue
*4)If you micro well-- You stay the whip for a few turns to maximize overlow
Other then that, whip everything.
As for the OP question, Monarch. Emperor I'm about 50/50. I play a heavily modded game that makes things tuffer though due to Better AI and Revolutions. Last time I tried a default game Emperor seemed a pretty good clip, ie it was a challenge, but I could still pull out a win. Overall I don't micromanage my cities enough, and still haven't really gotten good with the city specialization to move up to Imortal, but to be honest when you have to plan and do math like that, I find the game to be more tedious then fun, so I'll stick with the monarch/Emp level.