Forgive me typing in English, I don't speak Dutch although I can read it fairly well. 
This is a a broad questiion I know. I am coming to Limburg to research in person in June (I live in Australia).
What recommendations for where to look, what to see, what *can't* I get online. 
My family were mainly in Roermond, Helden and Venlo.
Thank you for any suggestions,