If you do take the slow roads be aware the the Netherlands has priority to the right in some areas of towns, and that includes for bikes. If you are turning know that bikes have priority over you and you must give way to them. On roundabouts it depends on local custom. Where I live now bikes give way to cars, where I used to live cars gave way to bikes, even on free lying bike paths around roundabout. If in doubt give way to a cyclist.
The name of the town/city is also the speed limit sign - 50, with many towns now having a big 30 zone in them too. Road marings indicate the speed limit on non motorway roads and the speed may nt be posted in any other way. You need to know those markings and know there are speed cameras all over, not always obvious ones. Same in Belgium btw, and their fines are higher than ours.
Find a website with the road signs and markings in English and gen up on them. This is a rather dry example, which doesn't include the road speed limit markings afaik.
Just found those on another Dutch site. Scroll down through the blurb to the pictures with the speedlimits indicated. Oh and bike tracks are generally red here, and always marked.

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https://auto-en-vervoer.infonu.nl/ve...msnelheid.html

Good point Hetismij; priority to cars coming from the right, unless otherwise indicated. And always always look over your shoulder when making a turn to check for bicycles going straight ahead, as these have the right of way!