You can only move certain portions of apps to the SD Card. The main file will always reside in the internal memory, and it's up to each dev to decide what else can be put into the SD card (most apps with external downloads allow those to go in the SD Card). The Note 4 officially supports cards up to 64GB I believe. I wouldn't get anything below a Class 10 for proper read/write speeds.
You can also root your phone and apply a hack to make your phone believe that the SD card is part of the internal memory, that way you can move more stuff that was once restricted to SD Cards.
Personally, I don't trust SD Cards as they're unreliable and tend to fail. Furthermore, my experience with SD Cards and Samsung phones has been less than ideal, so I stopped using them since the Note 3.