Open World Tools vs Standard Foliage tool

Olá, pessoas.
Talking about performance: the standard Foliage tool (Shift+4) have the same performance of the new Open World Tools?
I have this level with grass, bushes and trees painted with standard Foliage tool. I don’t know if worth it rebuild it using the new tools (Grass tool and/or Procedural Foliage Tool).
Another problem is that the new Grass tool only work with Landscape, and my level is a city (about 2x2 Kilometers, static mesh only). Is there a way to turn a landscape a placeholder? Just to use the new Grass tool on it, but not render landscape itself?

about the new procedural foliage placement tool, all it does is paint foliage. the performance should be exactly the same (but someone reported it was sometimes worse if made with the procedural tools). if you already painted your foliage you have no reason to delete it and use the new tool for that

about the grass tool, I might be wrong but I think they mentioned that they would add support so it’s not only for landscapes but also for meshes

nice scene btw