A mini-split does not use duct work to move air around.

The hole in the building exterior is to get the electrical and refrigeration lines between the units.

They come in a variety if sizes, with outdoor compressors set up to run anything from a single indoor unit to multiple units.

Do a search on 'mr slim' to see a popular unit.

In your case, the difference is pretty much the size. Other indoor equipment that could be matched to your outdoor unit would be mounted on walls or in the ceiling and use no ducts as brickeyee indicated

Go to Mitsubishi, Sanyo, Toshiba, Fujitsu and other web sites to see their consumer literature. There are good pictures and other information.