I believe Las Vegas is a hub for allegient. I live in okc and there is a nonstop from Las Vegas to okc which was the primary reason I chose it.
One personal item is free
Carry on and checked baggage comes with a fee.
When you book your flight make sure to decide then if you plan to have either checked or carry on because both has a fee and if you book it at the airport the price is higher.
Similar to southwest in that you have to check in before but it'll decide your seat, mind you some seat has extra fees.
Wish okc had more areas to go with allegient but it's pretty ok for a 2 hour flight. Not too uncomfortable for me and I'm in my late twenties.