Hi,
It is smart to take the maximum deposit bonus possible, as there are no wagering requirements to your original deposit.
E.g. you will deposit USDT -> you will get a bonus in BCD. While you play (wager) with USDT, BCD (bonus) will get wagered automatically and yes it can be withdrawn & swapped back to USDT. But please note that you will not get the full bonus amount straight to use.
-Dappcasino
As I noticed, for every level you have a minimum deposit amount! For the first level, which is 80% you need to deposit a minimum of $60, higher levels have a higher deposit bonus, but the minimum deposit amount is also higher! You choose how much money to deposit, and by that, you will get a bonus amount!
As Dappcasino said, as you wager you are unlocking your bonus! When you deposit you have your balance, but the bonus balance is locked! You are unlocking it by playing, take a look at this:
"Release amount = wager amount * game house edge * 20%".