This app was mentioned in 3 comments, with an average of 2.00 upvotes
I really wish I could tell you for sure, but I have not been back, and haven't used any other their other virtual lines in the past. I do know they are reserved through the Official Universal Orlando App
This from Universal's Website might help, but it would probably be best to call and ask.
I have heard though, that you can have up to 2 virtual line tickets at once, and after the end time, your ticket does expire and is removed from your queue. Also, the virtual tickets for Hagrids apparently go quickly and are reservable near or before opening
Jurassic Park has a good amount of the area under construction due to a new coaster they are build. Fortunately though, the River Adventure and Flyers rides are unaffected currently (past maybe some dirty water on river adventure).
If you are wanting to see the Wizarding world stuff, definitely suggest the park 2 park, and if you go in march, the express pass too (spring breaks and Mardi Gras celebration drives attendance way up. See here for crowd calendar estimates). Also the crowd calendar has opening hours, which might effect when you want to visit so you have the most time possible to enjoy.
As for park size and rides, I suggest downloading the Universal Orlando App so you can get an Idea of what you want to ride and wait times once you get closer to your trip date. Youtube also has some good POV videos of a lot of the rides and coasters to give you an idea and what you want to ride and what you want to skip.
Universal has an official app that has wait times for all their rides
https://play.google.com/store/apps/details?id=com.universalstudios.orlandoresort&hl=en