It is very difficult to tell the difference between ico scam and not but you can reduce the risk by checking the project team and the partners of the project.
how much profit does the airdrop make? talking about how much money is made from the airdrop depends on the fate and the number of your referrals because most airdrops currently use a random system and referrals. if you are still a beginner you should not participate in ico, just participate in airdrops and bounties.