Gambling wins on $1,200 or more are filed on a W2G not 1099. Gambling loses can be deducted up to the amount of the W2G win.
I have filed 1,000's of W2G's and no one ever asked to withold taxes at the time of filling them out.
Keno W3G's start at $1,500
Poker tournament W2G's start at $5,000.
No W2G's on live gaming wins.

1099's are used any time you win over $600 of a prize the casino puts up $ for.
No gambling loses can be deducted from 1099's.