>>9553139As a general rule, Playmobil is scaled for GI Joe (or other 3 3/4 figures) on their knees.
While some props and accessories will work great (I use things like the playmobil cash register, vault, camera, and most of the food props) with 6" and 5" scales (and some 3 3/4" scales) other things will be too cramped. (Their houses, for example, may be too low for your figures to stand in.
For figma, it's a per-case basis, some things will work and some things won't.
For nendoroids (and calico critters and so forth) the scale is actually close to ideal. Having said that, a nendoroid will feel more at home in a calico critter house than a playmobil house.