The "Heretic Queens Galore" situation is soon changing - I did more research on marriage legislation of 1690ies Commonwealth and realized that Sobieskis currently put themselves in the corner and Sophia is currently is in "have to compromise or have my marriage annuled, war consequences be damned" situation. Though being Sophia, she'll milk her compromise to whatever extent is possible.
Empire was adamant against female line succession in Silesia OTL. Don't think why this is changing TTL, but that's a spoilerific part for the first act of TTL Northern War.
The Duchies are in somewhat mediocre economic condition (much better position once the Industrial revolution starts), but those are big fat prize not only for the Poles - who jump for their piece of pie with varying degree of success - but the Silesian adventure will lead to quite the drop in Jakub I popularity and make him reconsider his foreign policy. BTW, in the next chapter Jakub gets... an interesting new friend, and the Crown Princess Ludwika is not going to be amused about it once she finds out.
That said, I rethought my idea about the match with OTL Electress of Saxony - his first cousin Elisabeth Albertine of Anhalt-Dessau fits better more agewise and because Duke Georg Wilhelm will be likely pushed to marry her once her education at monastery is over. Since the Sobieskis have already (and in OTL) married their relative to the one of House of Anhalt-Dessau (Duchess of Olyka is Elisabeth Albertine's younger sister), this match puts the Poles in better position for Silesian meddling once the time comes. And the OTL fertility record of Elisabeth Albertine is tailor made for succession crisis - 8 pregnancies but only one child lived past the age of 20.
Christiane-Eberhardine comes rather out of nowhere - Georg may meet her at court of his guardian the Elector, but she's still a toddler when he comes to the throne, unlike his first cousin whom he may marry right away. Christiane makes more sense to be married to her maternal first cousin Eberhard Ludwig, Duke of Wurttemberg (though IDK whether that would be much improvement over her OTL life in terms of family life/fidelity of husband). Or even to become a second wife of Margrave Friedrich of Brandenburg once his sickly Hesse wife kicks a bucket in 1690-1691 (the BEST outcome for her to be honest).