Not all ERC-20 shitcoin but majority of token are. It is because it has no high standard requirements in creating token in Ethereum platform.

You can do both and there are advantage and disadvantage of it. Airdrops are free but only few have a real value in the future. Bounty on the other hand had a big chance to have  value on its token or coin but you have to work for it for a specific period of time while airdrop only needs to fill up a registration.

Waves is a good long term investment like Ethereum, Stratis and Cardano. I hold it for long nd waiting for it to be fruitful like Ethereum when i bought it at 5 dollars each.

I will bet for WePower  because it has an active development from time to time and the project is really huge and visible. It is also very helpful and revolutionize green energy.

Airdrop and bounties are a marketing strategy so the coin they offer would be known in cryptoworld. Recently there are many airdrops gone bad because of many scams. Iwould suggest that you focus on bounty campaign but make sure to read investigate if it is worth the time.

I think one of the worst ICO is CarTaxi because even though the ICO is successful, the pice suddenly shoot down because of scam accusation of their campaign participants. Not a good communication with their investor is also one factor, that is why other investors dumped their token to avoid further lost.

I don't believe in ICO expert because they use it to hype people. Your own research is the best reference when you buy a certain ICO. It is your money, your investment and  your responsibility.