most of the casinos that require KYC have limits like if your deposit/withdrawals exceed 2k usd or 2k euro, depending on where the casino's area of jurisdiction. but yes, some won't publish their limits. in that case, if you are worried about kyc, try to contact their support what max amount you can depo/withdrawal without worrying their kyc. if you are abiding their protocols, you won't get any trouble, unless you win big, and the casino may possibly look at your account and start asking kyc before they release the winnings, which usually happens if the casino don't have much bankroll. if you are a high roller, i believe, you should always expect to submit kyc as your account may create flag under the AML laws.
I did not know that such limits are dependent on external regulators, but what you wrote seems to be very logical. However, I think that such information should be made public and not hidden, then everyone would have the full comfort of using online casinos.
On the other hand, if someone wants to play for such large sums of money, in my opinion, he should even negotiate the terms and therefore should contact the casino in advance to determine it.