Strange, I use it on the same setup and have no issues. I imagine you already know that the delay of the overlays can be reduced and eliminated in the settings. I recently nuked and paved that machine, though, and everything feels like it's running faster than before.

I'm not familiar with Wooshy, so I'll have to check that out. Shortcat doesn't receive updates and for years there has been an indication that it would move from beta to licensed software (which I would happily pay for!), so I live in constant fear that it's on the road to abandonware.