SPOG proportion help

I've read several times about spog rub for real texas style brisket/prime rib roast and many other a.
Probably garlic and onion are "to taste" but maybe I'm wrong.
Instead, for salt and pepper I know there are neat proportion but I've read different proportion. Probably this depends on the "GRAIN" of salt and pepper.
So at this point I asked for help.
I need a proved receipe for SPOG and for S&P (if proportions in this are different from SPOG ones) with clear and detailed instruction about the grain and about proportions.

In the Franklin's brisket video, it appears to me that He use the VOLUME way, but finally he used all the pepper "cup" and just a part of the salt "cup". Does it depend on ......?

Thanks in advance

I use equal parts, but just a little light on salt.

I used to use equal parts Kosher salt, course ground black pepper, powdered onion, and granulated garlic. But lately I use two TBS K Salt and one TBS each of Course Ground Black Pepper, Granulated Garlic, and Onion.