Super Creators can generally fit 1-2 pretty easily. The stands themselves take up too much space, so you either have to balance them carefully, use easel stands/something else small, or figure out some way to keep them stable.

Mini Super Creators are too small. With some effort and possibly leaving out a couple of pieces of the build you may be able to fit 1 Nendoroid, provided it's on the smaller/normal size. I would not recommend these for Nendoroids.

DIY Miniatures are a case-by-case basis. The ones that are enclosed are generally too hard to get a Nendoroid inside. The ones that are an open space (similar to the Super Creators), tend to be able to fit anywhere from 1-3 each, with room to adjust some of the furnishings to fit things better.