It has been some time since my last visit.

1) I assume AMS to Centraal Station is the same - buy a ticket @ AMS and that's it.
2) But for transit within the city, is it all tap/pay on the tram/bus, etc? Or is there some other sort of ticket required?

How are UBER and other similar services? (What others would you recommend installing?) I'm considering a car back to AMS at a relatively early hour.

You can tap on/off with contactless in all public transport, including the train from Schiphol to Centraal and tram/bus/metro.

This works great but also means you pay full fare per ride. You can download the local transport app or create an account linked to a contactless card if you want to use senior/children discounts or travel passes.
More explanation here: https://www.gvb.nl/en/customer-servi...oes-ovpay-work

Please remember to check in and check out as the lovely voice on the tram says! Otherwise you’ll be charged the maximum fares.

For the GVB buses, trams and Metro you can buy a range of day and period passes if you don’t want to get your credit card out every time you board and get off.

For the NS train again, if you don’t want to use your card then use their app to buy the ticket it will be € 5.20 and avoids the € 1.50 paper ticket fee if using a ticket machine. If you are travelling further afield if you book in advance via the app and travel off peak they offer discounts.based on how close in you book which can be quite substantial.

I’ve never used UBER always public transport. Even used the train last year between Centraal and Schiphol at 5am

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.