Before choosing which book sites you are going to play with remember that not all of them have the very same terms and conditions.
It's better if you are going to check each of the bookmaker's terms and condition since you said you are going to deposit and bet high stake some of them might ask you KYC.
And some of them might confiscate your deposit if you violated any of their terms so be careful and check everything before depositing.
All of the Casino has the right to freeze / block your money if you are violating there terms but they are not allow to confiscate your balance unless your account abuse there giveaways or exploit a bug on there Casino that result to your current balance but Casino is not allowed to confiscate your deposit money. They will freeze it but you can still claim it after sending KYC documents as AML requirements for dealing on this kind of situation.
I suggest staying away to all Casino that offers fiat deposit because they are the casino that has a critical license in terms of KYC for high rollers.