I think kits are one theme/room/category with like 12 or 13 items or objects all fitting within that theme. Take the country kitchen. It's only a kitchen set with one theme. Or the retro sportswear also one category/theme and comes with like 8 outfits. Then we have bust the dust which is vacuuming. It comes with a few different vacuums and gameplay. Smaller than a stuff pack related to one theme and category.
I still think we will get stuff packs as well. The kits will be more frequent than the other three types of packs to tide people over until bigger packs are released.