Why do so many people recommend waiting and essentially doing nothing for decades until you luck into getting the territories? Forming the Netherlands as quickly as you can is very powerful due to the free cores you get, since with them you turn into a cored 9 province power. It gives a serious boost to your military and economy so you can become a major European player before nations grow out of your reach.
Heck, forming the Netherlands before you start colonizing is pretty advantageous in itself. That means you won't get revolt risk in the colonies you owned when you did the tag change. If you developed a colonial empire as Holland and formed the Netherlands, have fun managing revolts until the colonies core.
Taking the two necessary territories through vassalage without CB costs 12 infamy. With CB, it costs 8. If you can't spare that, you're saying that preventing 4 BB is more important than getting early cores on 5 extra provinces. What justification is there for that line of thought?
Infamy = loss of merchant chance and compete chance = less money from trading.
Provinces you need = HRE. HRE provinces = .25 infamy per province unless it cores. So unless you have a higher infamy loss than .5 per year, you're gaining infamy. In the end, the amount of infamy you gain from taking those 2 provinces without cores (vassaling + waiting for mission that gives free core/claims on rivals/other missions that give cores) gives you 12.5 infamy per province, from the time that you take them to the time that they're cored. On top of the 6 you got from DOWing without a CB and annexing without a CB.
As a free trading nation, whose economy is mostly based on how many cots you can sit in with 5 merchants, that's
a lot of infamy. If you do go for the two provinces, sure you can form the Netherlands fast, and if that's what you want to do, great. But there is the loss of tech is quite large. In fact, when I'm playing Holland, by the time I start colonising everyone else in the world is around 2-3 levels lower in everything compared to me before I start colonising.
This is why people advocate "sitting around". You get a large head start on colonising, your military is near unstoppable and you have enough cash to afford everything.
Now, if you want a reliable, fast way to form Netherlands, it's a bad idea. Sure you lose out on some tech, but if forming Netherlands is your goal then just DOWing everyone you can while the Emperor is busy is probably best. I usually wait until I have a unit advantage though, as it doesn't take long for me to get ahead, especially when I'm pumping everything I have into Land tech. Temporarily grabbing military NIs first and then switching them later helps too.