Participating in bounty campaigns of famous managers only helps you increase your chances of receiving rewards, but does not guarantee that the project is good, the project will still become a garbage project as usual. But honestly, the projects in the bounty campaign are mostly junk, they can't even be listed on the exchange or will be dumped shortly after and disappear. I haven't seen any good or potential projects in the bounty board.
I think the best sure way is when the reputable manager do also escrow the funds. As long as the manager and the escrow doesn't turn into a scam then you guys can expect to get your rewards as soon as the contract is over. If some of the projects can do this then why not the others right? Although there are still legit projects who can pay even without an escrow and even if it's only managed by some newbie/unreputable managers.
If you are scared about the future of the tokens then don't apply bounty which pays their own token but choose the one that pays in stable coins instead or pays with top altcoins. There are lots of them nowadays.