Hate to say this but yes, you cannot trust a project but you can trust a reputable bounty manager, just as I have always done on this forum. The only times I have gotten "scammed" is when I participated in direct bounties that program people distributed. Every campaign I joined - including signature campaign like this one I still am in,,, I get paid when the manager is trusted and reputable. Track record and responsibility are very rare in this space. And they will not take charge of projects which they know are scam.
Sometimes even the project managed by the reputed managers will turn into scam and sometime the managers are also be a part of that scam project for instance aTriz is on of the reputed signature and bounty manager but he tries to scam the investors by giving fake credentials about that project but later on he ruined his life by himself so doing own research is important while participating bounties.
By checking those factors mentioned by OP, it will lead to a legit bounty campaign or maybe, not. You can find a lot of bounty campaigns where you can receive the payment (token/altcoins) which is the main reason of this thread right?
But the thing is there a lot of campaigns paid their bounty participants on time but there are only 1-3 out of 10 projects got listed there token/altcoin in the market and it even takes some time at least 4-8 months of waiting before you can trade those coins, so the rest are useless. That's why it's risky joining this bounty campaigns that pays token/altcoins that doesn't have any value yet, you will waste time and effort promoting those guys and get nothing.
Yes,you are right,even ater we got tokens from capmaigns it is useless dead weight until it get listed on excnage and most of the time it never get listed on anywhere so people need to be careful while doing bounty campaigns that is the reason I am not interested in campaigns which pays us in token or in altcoins.