I believe Spotify web helper is a separate process that acts as a minimialist web http server. I believe it makes it possible to use the play button and several interactions in the apps. If you remove it I think you will get problem with the web content (apps, play buttons etc.)
Is it normal that this setting reverts to being ON after installing an update?
I really don't want any unnessecary stuff running in the background. Surely registering a URI doesn't need a TSR in the background to work. I mean file, mail and even magnet URIs have never needed a separate background process to work for me.