I always use cocoa powder and not hot chocolate mix because hot chocolate is already sweetened and would make the truffles too sweet.
I place the finished truffles on a sheet pan lined with parchment paper as I roll them so they stay neat and do not stick.
I have tried using almond or cashew milk instead of condensed milk, but I usually need to add extra sugar since they are not as sweet on their own.
If I want to make milk chocolate truffles, I use a little less cream because milk chocolate has more fat and is already quite creamy.
If I do not use the microwave, I warm the sweetened condensed milk in a heat proof bowl over a pot of simmering water until it softens.