I very rarely ice or frost a cake, I figure that I have enough sugar in the actual cake I don’t need more. If I’m having visitors and I want to make something special then I will.
I never frost or ice a muffin, they just don’t need it.
If you’re making cupcakes an easy way to add colour and difference is to colour your coconut and sprinkle on top (It’s easy, food colouring and coconut, mix. Let dry and sprinkle.)
You can use sprinkles or 100s & 1000s. Yes they are another form of sugar but you don’t need as many and they are not as thick a coating on top as icing and frosting.
I freeze my cupcakes with nothing on top. I use the sprinkles when the cake is defrosted as sometimes the defrosting and condensation make the sprinkles soft and the 100s &1000s colour run.