During this period did the horse charge swords drawn or did they trot pistols drawn, and then sword fight?
They did both in the trot. Only Maison du Roi charged in gallop.
At Neerwinden in 1693 French Cavalry at the charge with sword carried breastworks covered by Infantry.
It's a myth. French historians admit that they followed Swiss Guards who breached the breastworks.
For some reason in the later period, the WSS, they reverted to firing with pistols.
Not quite reverted. They did it all the time. They used mix of cold steel and pistol fire in melee.
I know that Marlborough encouraged his cavalry regiments in the WSS to use the sword.
More precisely - to skip pistol fire. But they still charged in trot.
Bear in mind that real revolution in cavalry tactic was not abandoning pistol fire but charge in full galop. But to this one should have perfectly trained cavalry, because poorly trained troops charging in gallop can quickly become a disorganized mob. In the west (as oposed to the East - Sweden, Poland etc) the first army capable to do this was Prussian army of Frederic the Great.