PhD students regularly stress of selecting the "right" topic. But it is not something that you can know when you start. The important thing is to recognise that each change you make to your original idea is likely to increase the time it takes to complete your PhD.
Today, I was talking to some people about starting their PhD. One of the questions I get is “How will I know that I'm on the right track?”. “I'm doing the right thing”. “I've got the right research question”. Unfortunately, sometimes the answer to that is you won't know until you start your PhD, and you go down the road of interrogating the literature. Asking your questions you know, trying to find out how much is known about your intended topic. Sometimes, we can look to our supervisor or our potential supervisor as the person that should provide us this advice. But it's not always it's going to be them that's gonna be there for you to help you out to help you provide that advice. They won't necessarily know the literature in the way that you'll eventually come to know it once you do a search.