A full box opened yields roughly $150-250 in singles at current card prices, meaning you are paying $350-650 for the opening experience
Registering in the app is not required, but is necessary if you want to use the backup and sync features
Reprints add another layer of complexity
The goods news is that 75% of the mythics are worth more than the price of a pack (assuming you buy a box for $100 and not individual packs), so even if you don't end up a big winner, opening just about any mythic should be considered a small victory, which isn't true of many sets
Two of each is fine as well
//// Arcee, Acrobatic Coupe Color indicator: red, white Legendary Artifact Vehicle 2/2 Living metal (As long as it's your turn, this Vehicle is also a creature.) Whenever you cast a spell that targets one or more creatures or Vehicles you control, put that many +1/+1 counters on Arcee