We are there is 3 weeks also and staying offsite and like you I have had to ask questions and research it to figure out how it will work. In a nutshell, it's going to be much LESS convenient than you remember (machine at rides and tickets with times that weren't necessarily honoured so you could stockpile a bunch and ride using fast passes all evening).
Touring plans.com had a great explanation as well as detailed info on where the kiosks are and how many you can have but what you need to know is this:
As a non-resort guest, there will be a few fastpass ride times left (especially during March Break on popular rides) and the most anyone can have in a day is 3 total of any combination of rides. Resort guests have been able to reserve their ride times for a few months before they go.
Some parks tier the use so you can only have 1 fastpass for the whole day from a group of rides - it is not possible to have a fastpass for Toy Story mania and Rock N Roller Coaster in a day.
While it will be my first time trying it in 3 weeks, I have a plan to arrive for rope drop, ride the 3 or 4 best and favourite rides, get fast passes for the afternoon (when crowds are painful) and do shows in between.
They also offer fast passes for fireworks, parades and shows but this uses up one of your 3 choices for the day.
That is what I've learned so far. Not really a fan but maybe I will be when I see it in action. Good luck!