Ephs you cannot really have the "ultimate" formula because different people are constructed differently, mostly in the mix of fast and slow twitch fibers, and even for an individual the formula will be different for small muscle moves like Press vs large muscle moves like deadlift.
The "ultimate" formula is actually the collection of formulas and the knowledge of when to use one or another.
That's almost exactly what I was going to say.
I use a formula once in a while, usually when planning major changes in my routine, but for the most part, I know myself these days, and can do just as well guessing. The most important thing is what happens when you actually have a bar in your hands. If you can lift it X times with near-maximal effort, then that's your XRM.