Most of these allegations are an 'underdog story' that have little to do with truth, as you can read in this recent thread by u/wotan_weevil about the Tesla's achievements and his relations with other people, such Edison, Westinghouse or Marconi. In addition, you might be interested in this thread by u/khosikulu that gives an additional insight into the relations between Tesla and Edison. As for the development of electric devices themselves, you might also look into in my response to a similar question in this thread.