Bluebird promisifyAll versus promisifying each method

I am using a node module & instead of using PromisifyAll() I am creating a new promise object each time when I am invoking a method of that module.

This is a safe way to promisify?

If not then my entire code structure will change. So is it very critical to change or as long as I am using Promise its fine.

Also is there an impact on Memory or CPU if I promisify each method individually?

via Lajpat