Something to take into account is that SilverBullet is a local first web application, which is a bit unusual. It means that it syncs your entire space (all pages) locally to you browser, indexes them locally and then operates from there. Once this initial sync and index completes, this should all be fast (and it will be fully functional even if you don’t have an Internet connection), but the initial sync can take a bit if you have a lot of pages.
I don’t know what the upper bound of number of pages is, but my space currently has 1800 pages and works just fine.
In the past people have had problems with enormous spaces, often containing also large amounts of documents (PDFs, images). As of version 2.1 documents are no longer synced to the client by default, so this problems should be solved. However, if you have tens of thousands of pages… I’m not sure what would happen. Not sure many people use it this way.
I’m not sure if there’s a clear better way to go as to big pages vs many pages, not sure it makes a difference.