compound chocolate vs real chocolate
The difference is that compound chocolate is a low-cost substitute of lower quality than real chocolate. Accidentally, I am not sure that your "basic chocolate bar" is real chocolate either, the standard brands like Milka in Europe or Hershey's in the USA use a lot of foreign fats too. 

Is it a good idea? Only you can tell. If the compound chocolate is good enough for your taste, then it is a good idea (and don't let snobs tell you that your taste must be wrong). If you want the flavor and texture of pure chocolate, you'll have to use pure chocolate. 

If you want something softer than pure chocolate, you can try making a ganache, which also lowers the cost. But you can't dilute too much for a product meant to be picked with your fingers. 

You can generally mix different types of chocolate bars, including compound chocolate, without a problem. (I am talking of solid bars here, not ones like Bounty which have a nonchocolatey filling).