Hello @cranium!
Question 1:
opening several boosters.
Highly possible yes! Not implemented yet but I am seriously willing to add this in the next 2 days.
Question 2: transferring several cards at the same time.
Not implement yet and not high on priority list.
Several reasons, one being that it is mostly a feature useful to multiaccounts.
Before multi-transferring, there shall be one high priority feature: multi-selling (selecting several cards and setting a price X for all of them). This one will be very useful to all our players!