The Netherlands are a small, very urbanised country, with good public transportation.
So unless you want to visit relative remote rural regions, or carry tons of luggage with you, a car is generally more a burden than a joy. And an absolute nightmare in places like the centre of Amsterdam.
Almost all towns, also the smaller ones, can perfectly well be reached by train. See timetables on www.ns.nl.
When visiting large cities like Amsterdam : use metro, tram and bus. The old centres are made for walking.
In smaller towns and the countryside around : walk and cycle. Bicycle paths all over. Renting a standard Dutch city bike costs under EUR 10 per day. You always need to show an ID, and generally a refundable caution is required (often 50 EUR in cash). Bike rentals are often located in or near train stations.
With an organised tour, you are not supposed to have surprises with schedule or accommodation.
On the other hand, you're not free to travel at your own pace, to make your own choices. On a booked cycling tour for example, you'll have to carry on, rain or sunshine.
Having everything organised is probably wise for high season, July and August, in the parts most popular with tourists, and certainly in the seaside areas. The centre of Amsterdam is always busy, and there's the tulip season of April - May, in the coastal region south west of Amsterdam.
In the other regions, and certainly before and after high season, improvising and finding accommodation should not be a problem.