The best site for launching places is;
Campsites close to the river with launching however are few.
I know of one at Repps (near Potter Heigham). The staithe is a short walk and launching a Wayfarer looks ok.
This is also the best sailing area on the northern boards.
If you don’t have a license remember that you will need one to take your boat on the Broads.
Hope that helps