Rules of Cadet Branches & Succession Question

Say if Maria Magdalena (daughter of Leopold I) were to wed Aleksander Benedykt Stanisław Sobieski (son of John III Sobieski) and establish a cadet branch of Habsburg-Sobieski. Would the Habsburg-Sobieski branch be senior to Habsburg-Lorraine of Maria Theresia & Francis Stefan if everything else was the same as otl. How good of a claim with the Habsburg-Sobieski have to Maria Theresia's inheritance?
 
Two sons of Leopold I was first succeeded by his son Joseph I, who in turn was succeeded by his younger brother Charles VI (father of Maria Theresia).

Both Joseph and Charles left surviving daughters, Charles ensured that he was succeeded by his own daughter (and a daughter of Joseph). De facto in this case proximity of the blood was also applied.

In any case, no any house of Habsburg-Sobieski won't be senior, the most 'senior' cadet branch, is that branch most closely related with the senior branch, which a later house of Habsburg-Lorraine would be.
However maybe the ruler of Austria favours his/her Habsburg-Sobieski relatives to become king of Poland and Grand Duke of Lithuania?
 
That's be interesting, I was toying with the idea of giving Habsburg-Sobieski the Kingdom of Naples, So that Charles VI could take some other territories but that's also interesting. Would a PLC-Naples Union work, technically I was gpin for Maria Magdalena to be Queen Regnant in Naples, maybe Aleksander could be elected King of the PLC and if they have 2 sons the thrones be divided between the two (though there is no guarantee wining the PLC throne).
 
As far as winning the throne to the PLC, money talks and bull$&@! walks. I am sure there are some corrupt members of the Sejm at that time.
 
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