Grass here, grass there

As I have read through this forum, I’m not the first to ask this.

I have a house with some grassy areas around it, and made a well working grass for a nearby small area with a particle system. Now I want to apply this system to a larger area further away that now uses a simple mapped grass. But, since particle system starts with particle number, I would have to modify the original (increasing number of particles), thus I cannot use the original, etc. Questions:

-Is it possible to have a density-oriented particle system that can be applied to different objects (and thus reusable in different projects)
-In genereal, is it a wise idea to apply particle systems to objects further away? Is it a compute-heavy opereation?
-How others do this?