I'm not familiar with the pass and the restrictions that may come with the EP attached to it, but I can say that the express lines are almost always short. Many rides have separate dedicated ride vehicles for the EP line, or they pull from the EP line more frequently to load the ride vehicles. Seems like the priority is to clear the express line as quick as possible. We've never had an express wait longer than 15-20 mins, and even that is rare.
We've never considered the premiere pass, but I would suggest doing a price comparison. If you plan to buy an AP, no matter the level you get, one of the biggest benefits of it is that it comes with what can be significant discounts for on-site resorts. With a good discount, the three deluxe resorts that include unlimited express pass become much more affordable. Even if you don't need the lodging or don't want to stay at one of those resorts, people often book a "throwaway" room there for a night (i.e. a room they do not stay in or a room they just use for a break) in order to get each person in their party an EP for two days (check in and check out day). This is often the most affordable route. Alternatively, if you don't want to hassle with the resort, it may still be cheaper to just get the cheaper APs and then purchase EPs for your group on days you want them for. You can also purchase EPs day-of if you're at the park and its busier than you anticipate.