Although bounty activities are also full of scams, airdrops are almost always air projects that do not have any value.
Of course, there are a handful of good coins in airdrops, such as Semux and ACC are the only two exceptions and they are really good.
Seems like you have earned quite a lot with the way you special mention those coins above. I haven't earned that much and never really into Airdrops, joined a few and luckily earn just a couple from a single coin. While the others turn out into nothing but trash. I don't join bounties as the "Stake" term confuses me.