If Neverlost isn't showing on your charges then the Neverlost portion of your rental isn't guaranteed. Fortunately, many premium cars already come with NL so hopefully this won't be a problem for you. Most of the time they will upgrade you as well into a NL car if you have NL in your reservation.

Premium is usually a Grand Marquis so there is a huge difference between Premium (G) and Premium Elite (H). Avalons & Azeras are the two main cars that come to my mind when I think of H class cars. There are others, though but trust me they are all worlds ahead of the Grand Marquis.

Enjoy your trip.