In general you can use TS credits for a CS meal.
I don't know for sure anymore but there may be some cashiers who will tell you you can't.
As for using CS for snacks, they used to generally allow 3 snacks per CS credit at the resort food courts. There are now reports that they no longer do this (I personally witnessed a guy freak out when he wasn't allowed to do it at Captain Cook's this past January). There are also reports from those who were allowed to do it. There are also reports from those who were offered one snack, not three, per CS credit. Still others have said they could do it, but could only take certain snacks and one had to be a beverage.
So I don't think you can really know about the snacks for sure unless you ask someone actually at the restaurant, and even then the answer might depend on who you ask.