Hello don't do much saltwater fishing but have a casting reel coming which is saltwater approved with mono capacity of 12/100 if I were to spool this up with 30 lbs braid would that be efficient for light saltwater applications? And do saltwater anglers use leaders like bass fishing? Any advice would help greatly. Thanks!

O yea just for reference I live in nj and will be fishing at a bay outside of seaside I forget the exact name. There are blow fish, bass n American eel, nothing too big n that's all I really know are there, only fished it like three times

Pretty much everyone I have seen uses a leader in saltwater, swivels are very popular too.  30# braid is fine, I most likely would not use less than a 20# leader.  If it's saltwater there's going to be something bigger coming in at some point.