I view Castles & Crusades as an excellent 3rd edition of AD&D. Maybe I'm unfamiliar with the originally design goals and early discussions, but it seems to me that Troll Lords were trying to create their RPG (ala Palladium Fantasy), but compatible with TSR settings/adventures, etc.
As for the "best OSR takes", I prefer OD&D as the base because its getting back to the rawness of the primary text. Then, the authors can go in whatever direction they imagine versus being limited by what is expected by BX or AD&D.
However, my best advice to any OSR author is to ignore all the previous editions (as written) and just capture the spirit of YOUR game using whatever elements of previous editions speak most to you.
I reject the idea that every OSR book has to be "TSR compatible". It does if you are selling a retroclone, but if you're just doing an Old School-Inspired retro-whatever, then fly and be free.