Just went through your previous post again.
The lag spike of just the HP and exp bars decreasing/increasing, that’s how the software the game was made with works 
-
If you’re using any 3D sprite pack, that’s been known to cause lag for quite a few people. Try playing with just the default download.
-
If you’re not using any 3D sprite pack, try playing around with the different text speed as well as turbo speed settings in the options before backing up your saves, deleting and then redownloading the core.
-
Fiddling around the first two options when you press F1(or Fn+F1), turning off the battle effects in options, deselecting smooth mode etc,. Basically playing with lowest graphics settings.
The above worked only for one or two people, most people who reported sudden lag similar to yours(about 20ish people since the game was first released) despite having good computers couldn’t find a solution.
To answer this post’s question, a fresh install of Windows itself didn’t work for the 2 people I know who tried it though.
Sorry I can’t help you more 