If you have NS Flex Dal Voordeel, then indeed, you simply check in and board the train, and check out again once you've reached your destination. At the end of the month you will receive an invoice for the travel costs of that month, and the subscription costs for the next month. You can also use the card to travel by bus, tram and metro right away. Your subscription is not valid there, though, so you will always be charged the full fare for those journeys.

If you have Dal Voordeel on credit then you need to top up your card before you travel, or enable automatic reloading first. You then pay for each trip right away: a boarding fee is subtracted from the credit when you check in and once you check out it is settled with the actual fare. But also in this case you can use the card for all modes of transportation, again always paying the full fare when you travel by bus, tram and metro.

Depends-what you describe here is ONLY IF you have the FLEX variety, as there is still also the old-style ´on money=saldo´ variety. But nearly all newly sold such subscriptions are as FLEX-this means indeed you pay the subscription in advance and the fares (ONLY reduced if you check in in the off-peak hrs.!) will be encashed in the monthly bill afterwards-via direct debit. The ONLY thing the tiny screens will show is ´reizen op rekening´ so you cannot directly see what was charged-only later on your mijnNS account.

Yes, it will work for any other transport that takes the chipcard, but NOT with special (separate from the trains) subscriptions on such-only as ´pay when you go´-but the payment is afterwards.