If Sweden joined the Seven Years War on the Prussian side instead of the Franco-Austrian side, Sweden would aim to gain Russian Finland, Baltic Russia and the rest of the Baltics instead of Pomerania. It would likely be defeated by Russia, but the extra Prussian troops without the need to fight Sweden and Russia would allow Prussia to win the Seven Years War as in otl, but with Prussia using extra troops to allow it to seize otl 1764's Saxony's and Austria's territories. The Second Miracle of the House of Brandenburg would benefit Prussia and Sweden to the otl extent in otl and in this timeline.
If Prussia didn't invade Saxony in the Seven Years War, Saxony might be neutral or Austrian-aligned and the Seven Years War would proceed as in otl. The best case for Prussia would be Saxony supporting Prussia without or even with the otl Prussian invasion of Saxony and Prussia being able to recapture the pre-war status quo ante bellum and the rest of Austrian Silesia with better defensive and offensive positions to the Prussians and ending the Seven Years War with the Prussian victory as in otl by defending its status quo ante bellum pre-war and not having to exchange Saxony for the rest of Austrian Silesia and Austrian captured ex-Prussian territories. Prussia might make its victory even more tangible by taking territories (including Silesia) which were Austrian as of 1755 and 1764.
Sweden also regained its share of Swedish Pomerania as captured by Denmark-Norway in the Great Northern War. If Sweden lost that part of Pomerania, Sweden would still try and fail to to recapture Pomerania from Prussia in the Seven Years War as in otl, but with a failed naval invasion and retreat from Stettin instead of an unopposed reinforcement of Stralsund before a Prussian opposed invasion of ex-Swedish Prussian Pomerania. The long term effect would be Sweden gaining Norway in the Napoleonic Wars and Denmark retaining Pomerania in exchange. Since Denmark would have ruled Pomerania for more than 90 years, Denmark would insist on holding Pomerania and would keep it. In exchange, Saxe-Lauenburg and Schleswig-Holstein would become Prussian in 1815 instead of 1865 and Danish (ex-Swedish) Pomerania would become Prussian in 1865 instead of 1815.