While each dog will be different, the fastest way is to begin with crate training, and gradually expand the space in which your dog can be trusted over time. It’s possible to have your puppy somewhat reliable between 5 and 7 months of age. This is a very loose estimate due to differences in bladder sizes, feeding schedule and parenting.
No. Clickers are great for things such as teaching complex tricks because they can help you mark micro-movements by your dog. However, in my experience clients find it too cumbersome for general training of obedience. And it is not necessary since you are able to accomplish the same thing simply by saying the word “yes!” as your dog does something right!