Does anyone have any information (studies or white papers) that discuss the suggested minimum and maximum number of participants for ILT and e-Learning training?

Studies/white papers - have you contacted your local college's library? If you're taking any college classes currently, you probably have access to a wide variety of online databases of scholarly journal articles. Even if you're not a student, the librarians are usually extremely helpful and you can usually use the resources, even if you can't check them out of the library. I would start there.

I think you'll find that "it depends" is what it all boils down to. It depends on the subject matter, the experience of the audience, the number of facilitators, the skills and proficiency expected... It depends.