64GB should be plenty for that. You can always add more storage via micro-SD cards which act like a small hard disk if you need more.
You can't go wrong with 128GB if you plan to install several, very large programs.
I plan on getting a 64GB model myself next week.
I have a RT right now and have all of my documents, music, pictures, and videos on a micro-SD card and not using any space on the tablet itself. Plenty of room left and it is a 32GB model.