[parttimepro]

To answer the AA vs. KK question:
If you go all in with AA and get called by KK, you will win $200 81% of the time, and lose $200 18.5% of the time. EV = 200 * .81 - 200 * .185 = 125.

At Bet365, it's a little more complicated. Algebraicly, we can determine that the average EV is the bonus minus (wager requirements times house advantage). EV = 200 - (4000 * .005) = 180. There's a wide distribution of possible outcomes. You could lose your whole $200 or you could win $1000. Based on the earlier calculations, 15% of the time, you will lose money, and 15% of the time, you will win more than $380 (i.e. cash out $580 or more).

Bigger bets mean more variance, but they don't change the EV. In other words, if you bet $20 a hand, you'll have a much higher chance of losing money, but also a much higher chance of a huge score. The average is unchanged. Experienced whores make large bets to save time, because they know they'll do enough bonuses that the variance will average out eventually.

After you've exhausted the available cashable bonuses, you'll eventually go to the stickies, which are a whole other topic. Suffice to say that the higher your risk tolerance, the higher the EV for these bonuses.