The speed increase depends heavily on the complexity of the trees and the number of trees casting shadows to the current viewport. The performance difference increases a lot if you run a 4k screen like I do. In the video I show the difference going from 29fps up to 65 fps when WPO shadows are off vs on. When adding the Foliage Shadow Imposters in that scene the fps stays close to 65 fps with the non-WPO shadows on. So the increase there would be a 124% increase. If you add more trees it goes up even more. I have tested scenes in 4k where without this plugin the fps was less than 1 and with the Foliage Shadow Imposters added by the plugin, the fps was around 50.