after a few hours the new helmsman gets a bit faster on the tiller and figures out flat is fast.
Depends on the boat. Mine is fastest at about 15-20 degrees of heel. It does suprise me when someone who learned to sail on keel boat gets in a small boat and doesn't even think about easing the main or heading up when they start to heel a lot. But, it is just not something that is part of their experience.