No reason why you could not use window glass for plates other than the distortion of the lower quality glass that they use. It must be properly prepared as outlined in the book.
The emulsions described in that book for the most part don't use any form of sensitization and that is one factor that contributes to their slow speed.
At present, my emulsions are running at about the same speed as Kentmere graded papers for enlarging (AgBrI) and Azo speed (AgCl). This puts them into the ISO 25 - 1 range. The highest I have achieved is about ISO 100 with a rather difficult ammonia digest emulsion from an ancient text book on emulsion making. I'm working on a simpler formula.
Contrast ranges from 0 - 2 for the bromoiodide and 1 - 3 for the AgCl when coated on paper support.
Fog is low and keeping appears good, but then I usually use up the coatings rather quickly. The emulsion seems to keep in the refrigerator for months. Again though, I use it up rather quickly.
I have posted some pictures in the Alternative section.