When I was there in the mid ’70’s I saw Roach to ver 3lb caught on Voblex spinners and some Bream that would have weighed over 20lbs…..
Those Bream still live in my memory, if you’d have laid them on a dustbin lid (old galvanised type) they would have hung over the edges……staggering fish, and I don’t even like Bream.
You will find the Dutch people very welcoming and helpful towards you, just google up the nearest tackle shop to where your staying, give them a ring (they all speak good English) and ask them for advice, and ask if there is a local angler who could give you some on-site guidance when you arrive.
Their predator angling has some very strict close seasons and bylaws so a bit of local advice is the way to go imo.
Personally I would forget their river Carp, the rivers are huge and the megga sized barges shove up piles of water and the truely wild Carp have muscles and energy to match the currents.
I would go after Ide (a sort of Chub/Roach but a genuine predator) they can be caught on spinners and softbaits, but the locals are really the ones to ask.
Spro is one of their big tackle brands and the prices are 10% or more lower than here, and the sheer variety of brands is out of this world.
I know you will enjoy it, just wish I was going with you…..