How does Ripple and Tether play into moving funds between banks. I get Tether tries to keep its value the same as USD (USDT anyway). Ripple, I don't understand.

How does Ripple and Tether play into moving funds between banks. I get Tether tries to keep its value the same as USD (USDT anyway). Ripple, I don't understand... as the value per coin changes. So, how do you convert into Ripple and convert out of Ripple without risk of each coin rising or dropping in value? I'd like to see a mutual fund approach to transfers where the exchange rate is fixed for the day, so you know exactly what the exchange in and out will be.