is this an abstract question or you want to how much time take to move from exchange to exchange?
For ex eth might be fast in theory, but Polo will rarely load it faster than couple of hours
Yes, most exchanges using lowest fee possible mechanism. So don't expect many will broadcast them in lightning speed. Outdide of exchange, I using LTC quite a bit compared to BTC or ETH for the past weeks. ETh transaction seems back to more stable yesterday.
Ripple in theory not use for our day to day usage, it is created for the banking transaction in a nutshell. But that could alter if more people prefer to use it outside the traditional financial institution.