If you are flying in and out of AMS, staying in Amsterdam for up to 3 days, and likely to use public transport in the city several times each day, it may be cheaper to get the Amsterdam Travel Ticket than pay two train fares plus a GVB pass.

However note that the GVB passes are for multiples of 24 hours while the ATT is for 1, 2 or 3 calendar days, so it depends on your exact timings. The ATT is a paper ticket. You can pay for it in advance but there is not much point in doing so as you still have to pick it up. GVB tickets can be purchased and shown within an app (as well as on paper).

My understanding is that paying contactless on GVB services (i.e. no ticket required) is capped at €10 per day with no multi-day discount. A 24 hour GVB pass is €9.50 and 48 hours is €15.50. Unfortunately it is difficult to know what single fares cost on contactless, because they are charged on a flagfall and distance basis. Detailed planning would be needed to accurately work out prices in advance and is unlikely to be worth the time spent.