What are the differences between a fixed rate exchange and a floating rate exchange?

During a floating rate exchange there is a possibility that the cryptocurrency rate may change for the worse or for the better. Thus, the amount you receive may also change - you can get either more or less coins than expected at the beginning of the exchange.
During a fixed rate exchange nothing can affect the amount you receive which was shown to you initially. These exchanges are protected from rate fluctuations and any market changes.
There are no restrictions for floating rate exchanges. However, setting upper limits is a necessary measure for fixed rate exchanges since we take all the risks of cryptocurrency volatility and this risk grows with the amount of coins.