In general, these regimes have been able to coexist with fixed exchange rate regimes, and to do so relatively well in a world of open capital markets. However, the success of this coexistence has depended on countries following "the rules of the game" appropriate to the exchange rate regime they have chosen. What do I mean by "the rules of the game"?
For countries with a flexible exchange rate, this means that authorities should actually let their currency float freely. And for countries with a fixed exchange rate, this means that authorities need to run appropriate policies in order for the fixed exchange rate to be sustainable.