Quick note: I was doing some more testing, and while the foliage is performant with at least a couple hundred copies in a scene (using a more complex collider too), I found I was able to get some performance hitches with only 3-4 in a scene if I passed through them with the player character in a way godot didn't like. The fix I found was just switching the physics engine to Jolt, which you can find in the Asset Library, and I haven't been able to generate a similar performance hit since switching.
Quick note: I was doing some more testing, and while the foliage is performant with at least a couple hundred copies in a scene (using a more complex collider too), I found I was able to get some performance hitches with only 3-4 in a scene if I passed through them with the player character in a way godot didn't like. The fix I found was just switching the physics engine to Jolt, which you can find in the Asset Library, and I haven't been able to generate a similar performance hit since switching.