Over $600 prize money comes with a 1099.
Prize money meaning money the casino put up.
It is over $600 for the year. If you win $400 once and $300 later, you get a 1099 for $700.
No, you can NOT deduct loses from 1099 money.

Has nothing to do with player funded tournaments.
Player funded wins come on a W2G. You can deduct loses.
Poker tourny wins after March will have to be over $5,000 before a W2G is required.