Regarding the payment methods:
Each currency will be upgraded using the current Bitcoin / Litecoin / Dash rate.
If we take the example regarding the bitcoin:
This will be converted automatically. If you have your balance in USD, and you make a payment of 0.5 BTC, the value in the balance will increase by half the value of the Bitcoin.
Suppose the Bitcoin exchange rate is $ 18,500, and you make a payment of 0.5 BTC, your balance will be $ 9,250.
This value of the fiat remains intact in your balance sheet, and the price increase / decrease has no influence on it.

When we have implemented multiple payment methods, you can request a withdrawal from the method that also included a deposit. Bank transfers are always possible in any situation.
If you want to withdraw funds to a payment method, then you have to make sure that you have made a deposit with this payment method before in order for us to approve the withdawal.