Chocolate – What kind of chocolate should I use to coat homemade turtles

If they are crunchy when frozen they are probably made from regular compound chocolate, not freezing grade chocolate

You should be able to buy compound chocolate "chips" from any food wholesaler or baking supply store. They are the same as used in chocolate muffins

For frozen chocolate to still have a chocolate feel and taste when eaten it needs to be made with peanut oil (or similar) so as to have a melt point more like chocolate at room temperature when frozen

Regular "Real" chocolate can end up being like eating crayons

Real chocolate with a low cocoa butter, but high cocoa solid level generally freeze much better

Chocolate chips often come in 3kg or 5 kg bags, if you are not using them in a hurry, keep the surplus in the freezer :-)

I would say yes. However, depending on what kind of squares it calls for it may change the taste of the brownie or how rich the chocolate flavor is. 70% cocoa bars would be more similar to what Baker's Chocolate sells as Bittersweet (67% cacao) so if the recipe is calling for Unsweetened squares (100% cacao) then you'll have less chocolate flavor (and perhaps a slightly sweeter brownie). If the recipe is calling for Semi-Sweet squares (54% cacao) then you'll have more chocolate flavor (and perhaps a slightly less sweet brownie).