In order of preference, option 4, 1, 2, & 3. I realize I've put the long-wait ones first, but those would be very interesting to get the details on as a grand historical view.
I admit to being very curious to see how different the Mediterranean world becomes with a united Spain untethered to Austrian interests, and having drastically altered the course of trade and commerce with the effective elimination of large scale Barbary piracy. It seems as though Spanish concerns about the Ottomans would be related to its Italian interests, (with religious motivations as a less practical concern) with the relationship to Austria being simply one of pragmatism. That would seem to open up a lot of potential for a closer Spanish relationship to Poland-Lithuania, Venice, etc even to the point of Austria's disadvantage. A lovely venue for diplomatic and political scheming all around!