To choose a bounty compaign, I advise you to look at the status of the manager on this forum. The higher the status, the more reliable. This does not give a 100% guarantee, but most of the scams come from managers with the status of Newbie.
See the ICO rating on sites such as ICOBench and others. Do not join companies with a rating below 60% (3.5 on ICOBench).
Do not join the company from any managers from Amazix.
P.S. In choosing a bounty, this free table can help you:
https://docs.google.com/spreadsheets/d/19fLkDCH0E4uOrYlgqAVixmCIOGupLl8cLRlwttvXsT8/edit#gid=0Yup, I agree with you, the rating of the managers that handle any bounty campaign is a good thing to take into consideration before joining but it does not give guarantees which is why further research about the developers and how common or rare the concept of the project is is also very vital in choosing the right county campaigns(at least that's what I think and do).