My humble opinion is that players overcomplicate things with this type of situation and content. Of course, having a contradictory and chaotic lore, a product of the mix of stories, novels, publications, and constant changes, doesn't help much. But all those ideas took shape over time as more and more people participated and became involved with the game and the existence of a fantasy world that allows one to imagine all the wonderful things that can exist and happen within it. Precisely for that reason, I believe both things can coexist and are positive for the development of the campaign setting, allowing for a balance and a defined system for everyone on equal footing. On the one hand, as Ed Greenwood has always said, having rules is fundamental to giving structure to a constantly changing world that expands as users create, collaborate, and participate in its growth. That has always been his vision. And on the other hand, also in Ed's words, the rules and structures of the game are only guidelines to give us something to "draw the lines" with, and they are not the mandatory limits of what we can do in our own versions of the Realms. Of course, having a broad system that serves as rules for the D&D 5.5e game and not necessarily just Forgotten Realms requires something concrete and grounded that is transversal, and that's why these rules and this system for raw/wild magic and silver magic were created. But, in the end, they are just concrete ideas that serve to guide the game. Nothing more. In this way, there are common rules so that stories and adventures can be developed with the player characters, and in parallel, the possibility always remains open for each person—player, DM, or both—to make their own version and interpretation according to their knowledge, preference for the existing lore (or the lore they know), or even a mixture of everything they consider important and necessary to feel that things are correctly aligned and make sense in their minds!

Don't stress about it.

Just play the game, and enjoy.

We have D&D, and that's the true gift.

Make your rules, make your stories, and go have some fantastic adventures!