Normally, you should find the answer to all your questions in the terms of service or the frequently asked questions pages. This is another sign that the casino is decent enough and can be trusted because it means they care about their customers by offering them answers to all their questions publicly and don't hide any information.
But regarding the max amount you can withdraw, there shouldn't be any limits because it's your money and you should be able to withdraw it all if you want. For small casinos, they may pay you in settlement if their bankroll is not big enough.