There are so many bounty campaign that moderate by newbie with 2/3 activities, is that kind of bounty are safe and believable?
It is difficult to say in a word. But it can be safe or not. You have to decide by seeing the project details because it is open for all and none will force you to join in the bounty campaign. So you have the chance to research which one is good and safe. It doesn't depend on the rank of a manager I guess. Just take a look on the project if it seems legit to you then go for joining that bounty campaign.