What are your approaches to finding manuscripts online

[ReneZ]

When it comes to archives, I have two questions. Not rhetorical ones - actual questions.

One is about the Vatican archives. What is in there, how much is "hidden", how much is digitized, how well-known are these scans? How accessible is it to researchers, and how many manuscripts are there that have not been touched by anyone who had Voynichese in their accessible memory? 

I don't have a good overview, but from my limited experience, I would say that archives are generally not digitised. This is independent of the question whether any such data are available online, either publicly or only to selected users.
Digitising requires manpower and dedicated funding.

Preservation (by making copies) started well before the digital age, and there are large collections of copies kept on microfilm, usually black and white, and stored (far) away from the originals. Again, this would be of library items much more than archival material.

Archives generally can be visited for research, and Mark Knowles has written quite a bit about that.
However, this is barely a feasible path of research for Voynich enthousiasts for several reasons:

- the material contained in these archives can be vast, and just visiting for a day or two will allow to see only a small fragment. (You'd need to know exactly where to look, which brings back the point of the knowledge of the archivist)
- it requires training to be able to read and understand much of the handwritten material
- without a deep knowledge of the historical context, one is likely to miss potentially important leads 

This last point may seem strange, but it is based on my own experience. This sensation of: "I wish I had known 'this' when I was 'there' ". 
 
With respect to the Vatican, as I am sure you know, they are digitising and publishing the vast majority of their library collections. Some of these collections have 'archive' in their name, but that does not mean that their entire archives will be published online.

They also have guidelines. For example, and I don't remember where I read it, material that is too 'recent' is not published. It may not even be accessible except to documented researchers (letter of introduction). 
Other collections will be generally protected.
Note that the italian word "secreta" in this context does not mean 'secret', but 'separated'. That may still mean: inaccessible.