there is an other option available with `-gridDist` which reads grid spacing. It allows for non-equal distributed number of cells over different nodes. I tried to describe it in full with `picongpu --help`:
```bash
  --gridDist arg            Regex to describe the static distribution of the 
                            cells for each GPU,default: equal distribution over
                            all GPUs
                              example:
                                -d 2 4 1
                                -g 128 192 12
                                --gridDist "64{2}" "64,32{2},64"
```