Agree that it is interesting to think about how Bird would compare with massively increased training schedule, sports medicine, practicing three point shooting a TON more, ball handling practiced/carry tolerance that would be able to break down even G League defence.
That being said, his high volume 3 point shooting years, he is remarkably accurate - Curry level.
So probably fair to presume with waaaaay more reps and modern conditioning he could be the best 3 point shooter in history.