Well, would you say that there is a slight difference between "clothes" and "wardrobe"?

Well, in English "wardrobe" (and Polish "garderoba") may in fact mean a collection of clothes, but "szafa" is definitely a place where you store them, and noc clothes, which are "ubrania".

szafa=wardrobe as in piece of furniture

garderoba is 1) wardrobe as all of the clothes that a person owns
2) a changing room backstage
3)a seperate room dedicated to storing your clothes , a walk in closet