Nowadays, you can simply check in and out with your debit or credit card and pay the same fare as with an OV chipcard. So no need to worry on charging your chipcard (which is easily done at a ticket machine).
As you're arriving by plane in Düsseldorf, you'll still need to get a ticket for the German part of your trip. Tickets for IC and ICE would be bound to specific trains and routes in Germany. But as you are going to Eijsden probably the regional train to Venlo from Düsseldorf is the most practical option. I believe vrr.de offers options to buy a ticket online, but they are also easily purchased from the green ticket machine at the station.
You'll need a preisstufe D ticket to get to Venlo AFAIK.
It's also possible to buy an international ticket from Düsseldorf Flughafen (or Hbf) to Eijsden through Deutsche Bahn.
I think it is wiser to buy a ticket to Maastricht. When you do have to check in at Eijsden you need to leave the train and to check in at the platform. In Maastricht there is sufficiënt time to do so.
I have a (probably) silly question. I am travelling from Dusseldorf to Eijsden this Thursday and I was thinking about whether buying an online ticket in advance is a good idea. The thing is I don't know and can't remember how to load an OV-chipcard. And is that better than an online ticket? (I have only used it for subscriptions in the past). Can it be used as a debt card for all means of transport? And also when booking a ticket for a specific route, is the specific hour indicated or only the date? (bec. I am afraid of any possible delays of my flight).
You can't use a contactless payment card or a Dutch chipcard to travel in Germany.
An international ticket is (almost) always valid for a specific border crossing. Whether it is valid for a specific train (departure time) depends on what kind of trains you book and what kind of fare you choose. For flexible fares though, it often doesn't make a difference if you buy in advance. If you could mention the concrete connections you'd use (depending on your exact arrival time), then we could advise what's best (cheapest).
