First of all keep one thing in mind that bounty itself not enough for earning if you considering it as primary source. As no guarantee that project will succeed or even list on exchanges.
Now for chooding right bounty you need to filter projects thinking you are going to invest your money in that (time=money) so do good research on those projects and select best out of them.
one more thing suppose you find 2 projects, one project with great idea and high chance of success but low payout in bounty, 2nd project with high payout but almost shit project. then choose the 1st one because many time i have seen shit projects offer 2-3m usd worth tokens for bounty but if they are not able to list or raise even soft cap then you will have bag of tokens without any real value.