This will probably answer those questions in detail:
http://www.shrapnelcommunity.com/thr...=&fpart=1&vc=1
To answer your question directly:
It's most efficient to hunt with a B2 mage (or a B1 with a dowsing rod) in a province between 6K-5K in pop.
I've found that 3 B2 mages in 5K pop provinces with taxes set to zero seem to work the best.