Contemporary online casinos are pretty flexible in terms of deposits and withdrawals and offer at least 20 payment methods to choose from, including country-specific ones. However, most payment methods have limits incompatible with the playstyle of the high rollers.
The most viable option for high rollers is the bank transfer as you don’t have to adhere to any limits. Depending on the casino you play at, deposits and withdrawals to a VISA/ MasterCard can also work. As for the e-wallets, Skrill and PayPal should suffice.