Well, if Catherine II chockes on a sausage (of one kind... or another) before 1792, you'll get a PLC with 3 May Constitution still going on, while Napoleon is gathering steam. Existing PLC also makes possible that Russia under Paul doesn't join any coalition, so there won't be an Italian campaign 1798-1800. Or PLC is forced to take part anyway. Nonetheless it may end with French-aligned Poland up until the Continental Blockade. I don't see PLC being any happier about it than Russia OTL. So instead of 1812 Russian campaign, we get 1812 Polish campaign, ending with sth like mix of OTL Spain and Russian campaign, with Russians playing the role of the British in this scenario. Then sooner or later we have Prussian side-switching, German and Austrian side-switching with end result similiar to OTL, but with PLC on winning side and back (mostly) to pre-Partition borders.