RealGM

Ok in Football I know if Vegas knows that Az will beat the cowboys but at the same time they know theres 1 billion crazy diehard Cowboy fans that are love blinded by their team.
I heard they may still set the spread in favor of the Cowboys at a smaller rate but like +1 or +2. this will bring a billion dollars in bettors lining up to bet on the Cowboys. Once the Cards win they may have a few million to payout but the vast majority of money was made by the house.

Now in basketball do you think to an extent they do that with the Celtics, and Lakers. Because the denial rate from their fans that their team could lose has to be a factor wouldnt it?
If your going to beat the spread wouldnt you ultimately watch these teams the most?
or
Watch the least favorites in Clippers, Bucks, and Grizzlies. Then knowing that the mass majority of people bet against them because of their history>?

If your looking to beat the spread would you do it on winning/losing games or total pts scored?

That's not how it works. What you're describing is essentially the house gambling on the game. In your example, if the Cowboys win then the casinos lose a tremendous amount of money. What the casinos in Vegas actually attempt to do is balance the total value of the bets coming in on both teams.

When too many bets come in on one team, the odds makers manipulate the betting line and/or the pointspread to encourage people to bet on the opposite team. To use your example again, the betting line for the Cowboys/Arizona game might start with a pointspread of Cowboys +1 and a line of -110 Cowboys, -110 Arizona. But a lot of people start betting on the Cowboys, so they move the line to -130 Cowboys, +110 Arizona. This means it's more expensive to bet on the Cowboys and cheaper to bet on Arizona. As they continue to move the line, more people end up betting on Arizona because it represents good value and the value of the bets on either team becomes balanced. They tend not to move the pointspread unless absolutely necessary, because it exposes them to risk from people who bet on both teams at different pointspreads.

It's not easy to balance all the incoming bets, but done properly it has the effect of strongly mitigating or altogether eliminating risk for the casino and ensuring a profit.