A quoted APY is not a promise of future returns.
From what I know in most DeFis, the quoted APY is historical performance, it tracks how much return from yield has been distributed so far against the capital, averaged out. It's just an indicator for what the users might receive in the future based on past events. In some case, quoted APY is simply pool rewards divided by pool participants and it's usually volatile. Not a promise of future return, but you could make estimation. I'm sure if it was based on historical performance the result usually wouldn't be too far off.
Regarding comparing net yield and the risk, it's pretty hard to say. Every project have their own risk. You're going to need to look into the risk involved with how they generated the yield such as risk of losing if the yield is coming from arbitrage or market making. For LP, you will need to look into each token pair, etc.
I do not think that staking yields a high return. For instance, if someone stakes $10,000 SOL for one year, the total return would be $500 which averages out to $42 per month. When compared to the capital involved, it is clear that any trader could easily generate $42 per month through trading, assuming a starting capital of $10,000.
Also +1 on this, staking anything below $50k is usually waste of time unless that person is staking while also expecting capital gain from price appreciation. If I'm holding Solana after I'm buying it at the bottom and expect it to rise within 2-3 months, I'd stake it to earn yield while waiting. This could turn staking below $50k from just a waste of time to a good passive income.