It’s SOOOO much easier to play the Ruy Lopez as Black than it is as White. There is no “mainline” in the Ruy Lopez. The closest thing to it is the Closed Morphy, in which there are like 10+ solid variations each with their own respective ideas, but the Closed Morphy has fallen out of fashion with the rise of the Marshall Attack, in which there are a plethora of complicated ideas, but you also have to know how to play the Classical, Berlin, Arkhangelsk, Neo-Arkhangelsk, Cozio, Old Steinitz, Modern Steinitz, Open Morphy, and Schliemann, none of which only follow one theoretical line. You could, as White, opt to play the d3 Ruy Lopez, and accept the worse position in exchange for a much smaller theory book, or you could play the a4 Ruy Lopez, and accept the slightly worse position in exchange for a slightly smaller theory book, but all Black has to do is have one answer for each of these, and they’ll always have much more experience in their lines than you will.
All im saying is that the "Ruy lopez: Masterclass edition" course is right there for free.
It’s SOOOO much easier to play the Ruy Lopez as Black than it is as White. There is no “mainline” in the Ruy Lopez. The closest thing to it is the Closed Morphy, in which there are like 10+ solid variations each with their own respective ideas, but the Closed Morphy has fallen out of fashion with the rise of the Marshall Attack, in which there are a plethora of complicated ideas, but you also have to know how to play the Classical, Berlin, Arkhangelsk, Neo-Arkhangelsk, Cozio, Old Steinitz, Modern Steinitz, Open Morphy, and Schliemann, none of which only follow one theoretical line. You could, as White, opt to play the d3 Ruy Lopez, and accept the worse position in exchange for a much smaller theory book, or you could play the a4 Ruy Lopez, and accept the slightly worse position in exchange for a slightly smaller theory book, but all Black has to do is have one answer for each of these, and they’ll always have much more experience in their lines than you will.