Do you have to pick a "Exective Area" rental to use it?
 

I'm booking a pick up in LAS, the options between a FS which shows executive and a Premium is not much... I generally like to be able to pick FS SUV and sometime when request to pay extra for a premium SUV the class I book matters how much they are willing to sell me the upgrade form. Curious if it's worth booking the premium in LAS?

So long as you pick any midsize vehicle, you'll get access to the Emerald Aisle and whatever may be in it. Now, if you pick a Premium class, at the very least you'll be guaranteed one of those vehicles.

As for whether it's worth it to book the premium in LAS or chance it, I would recommend checking out the LAS Location thread, it's not perfect but should give you some idea of what to expect at this time of year.

To OP: no, you can book higher than fullsize and have access to the aisle too.

I’ve also had luck picking FCAR and below from the Alamo side with a National reservation. They share the fleet. Sometimes nice cars are parked in the Alamo side because the National aisles are full.