I just want to clarify, because there are several people offering their advice, but are misunderstanding what I'm looking for.
Imagine you import a Megascans collection of small rocks, they are all separate (unique) objects and all import at transform (0,0,0). Now arrange them in a grid.
I'm looking for a script that does this, as MCG_Arrange does, with parameters to arrange the objects in a grid of arbitrary number of rows and columns. For example, if you have 16 objects, you could create 2 row/8 col, 8 row/2 col, 4 row/4 col, 1 row/16 col, etc.