Gras meshes are supposed to cover at a minimum 25cm squared. (Best case use a circle with 25cm diameter)
You should have several different grass meshes to use in order to get a natural varied look.
Also, 2 separate outputs so you can paint the smaller size where you need to - on peaks and other places where the larger meshes have a hard time aligning to the terrain because they are too big.
If you already know that your terrain is mostly flat. You could go with up to a 2m grass mesh.
the problem comes when painting the details of where grass isn’t supposed to be.
using a 2m mesh you would first have to use a different grass layer for a smaller mesh, then remove the procedural from the areas you don’t want it on, like on dirt, where the Alpha value of the paint will cause it to spill.