I use webdriverio, which has pretty straightforward screenshot plugins. Honestly early on it's better to focus on API testing. My advice is start small for the UI and focus on a few critical components like page routing or features that would be a show stopper if they broke. I don't think screen shot tests will be of great value if your product is not very mature. When I first started I made the mistake of blindly following my predecessors user stories that weren't particularly well thought out.