On the first point: There used to be central sites that listed airdrops and ICOs. However, these are no longer reliable because the number of projects has truly exploded in recent years and it is simply difficult to keep track of them all. That's why you need to keep track of multiple sources yourself. I would recommend you to regularly search for the keyword "airdrop" in Google or Twitter, then you will get a rough idea of what is coming soon. There are also some blogs that specialize in this.

To the second point: Airdrops are hardly worthwhile today and I would leave my fingers from it. Especially if you don't have bigger stakes in major projects yet. Serious airdops without having stakes so far bring only a few dollars and usually you have to do a complex KYC, simply because such projects are regulated today.