studying the lower schools to understand this topic is almost useless, since they dont even know how to posit direct perception of negatives ie. they are always implicitly known.
they are uselful to study only for people who are actually on the path of preparation and want to compare the precise and subtle machinations of their meditation, whereby these manuals become extremely subtle and precise historical accounts / guides.
the best and most complete tenet book is translated by jeffrey hopkins: Maps of the Profound
also check: http://www.berzinarchives.com/web/en/ar ... advan.html
according to the gelug position which uniquely asserts that emptiness on the path of preparation is actual emptiness, the beginning of the path of preparation is what the mind-only school call the path of seeing. so the vipashyana is extremely strong and conceptuality is extremely subtle relative to us, but still very coarse relative to actual emptiness (ie. absence of ignorance and conceptuality)