You are able to increase the angle to the right or left as long as the fletch remains in full contact with the shaft. You must pay attention to the diameter of the shaft, because the smaller the diameter the shaft the less angle you can have to your fletch. The larger the diameter the shaft the greater the angle you can have to your fletch. This also means that you must reset your jig when fletching different size arrows. Feathers will require you set up the jig in a different way than vanes.
Feathers have a base on one side only.
Vanes have a base on two sides. Vanes are manufactured straight so they can be fletched either with a right or left wing angle. Feathers have a natural curve to them being right wing or a left wing curve. You must use only right wing feathers to have a fletch angle to the right and left wing feathers to have a left wing angle. Obviously you cannot mix right and left wing feathers on the same shaft.