express passes all go to the same line. but there are 3 ways of getting them.
1. buy them at the park. they're good for 1 trip into the express line for each attraction.
2. every ticket holder can use the express kiosks much like fastpasses. you put your ticket in, pick a time, and come back at that time to get into the express line.
3. resorts guests just flash or scan their room key to avoid the above.
there is no 'FOTL' line itself. UO advertises 15 minutes or less for express and 99 days out of a hundred, they deliver. when the parks are packed, they do their best. Shrek has a resort guest line that isn't advertised. they're also in the process of opening a whole new theater to accomodate the crowds. you're in a much better position staying onsite. but anyone can utilize the free express pass option. but there are a limited amount of tickets for each time slot. from what I've seen, the price of the express booklet is based on projected park attendance for that day. I may be wrong about that.