What to do with the Balance and NC pins?
I looked at the TI datasheet and I don't see anything telling the user how to deal with the balance terminals if untrimmed Vos is acceptable. Maybe you can figure it out from the schematic, maybe not. Since TI bought NS that is the official datasheet of the original manufacturer (the go-to document). I think you would have  avoided the two downvotes (as of this writing) had you linked the datasheet pdf and indicated its silence. 

The general rule is that if the datasheet doesn't say anything about the offset null/balance terminals you can leave them open if unused. I don't know how you're supposed to know that except that it was explicitly stated early on (at least for similar vintage op-amps).  

NC usually means that it's not connected inside and you can do what you like with it (like leave it open). Usually if it's internally connected to something you should not muck with they'll use DNC  (Do Not Connect), but always check the datasheet thoroughly. It  is not a nice feeling to find out that a PCB needs to be respun because something was missed.