Whether or not an infinite number of particles will fit or not is not important, no ? I’m not sure what you mean by finite granularity. There is no “grid”, space is continuous, the planck length and the fact that push on each other doesn’t really factor in. By virtue of space being continuous and particles being finite, means you can configure stuff in infinite ways.
Edit: Not quoting you with the reference to a grid. I know that’s not what you mean.