They can both play a bit of an impact, but I'd say connection speed will be a bigger factor, especially if you have the app opened and waiting for 10am. after the app is open, it's mostly about getting the connection to Disney servers to pull in the data you need for the BG.
BGs being gone in 15-20 seconds has been the norm since re-opening.
The park opens around 9:20 in the morning and some rides are operating before 10:00 a.m. so some people have been able to ride before joining or join a boarding group while on a ride
I got into the park last Monday around 9:20. Got in line for MMRR inside the building. Was off the ride by 9:45. Your mileage may vary.
get on MDE minutes before 10am, hit the join button on the front page and hit again when your group populates the screen.
Definitely practice a few times before heading down to get used to timing and button clicks. The boarding groups are gone in 10-15 seconds, so knowing the clicks before will save you time
No need to lug your iPad Pro around just to grab a BG unless you just want a big screenshot of your BG number..
The key factor is practice, practice, practice. Quick fingers hitting familiar buttons is next and a reasonably solid connection could be either Wi-Fi or Cellular data. Just find a spot to stand still for the 30 seconds to get set for the clock to roll over to 10 AM and once you grab your BG in 10 seconds you are free to move about the park...
You can uber or drive your own car, i would not count on Disney transportation, or if being on the park by 9:20 is important to you to ride attractions then you could walk from the epcot resorts
