Many archives or other repositories will have an online archievenoverzicht, a listing of their collection.
The word archievenoverzicht literally means “overview of archives.” It will give you a list of the collections, usually organized by categories like population records, court records or tax records.
Some archives will only have the archievenoverzicht online, but most will have the finding aids (inventaris) for the underlying collections as well. That will tell you which records are held in these collections. And if you’re very lucky, the digitized records themselves will be on the website. I estimate that less than 5% of Dutch records are available online as scans, but probably at least 50% records are described in finding aids so at least you will be able to find out if a record exists and where to find it.
Searching for the word archievenoverzicht combined with the name of the town where your ancestors came from on a search engine like Google may give you an overview of records that are available for that area.