I could see a proven engineer #1 with a track record of startup success maybe landing in the 5–10% range (but getting an under market salary), but otherwise I don't see how a number like that is possible. YC takes 7%, and if the first few hires each get 5–10%, that only leaves ~70% for the founders and subsequent hires. If there are 2 founders, they would end up with 25–30% each, and if there are 3, only 15–20%? The numbers only get worse if they've already raised a funding round in return for 20% of the company.

These numbers look more typical to me: https://www.holloway.com/g/equity-compensation/sections/typi.... The article mentions that hire #1 typically gets 2–3%, and only more when it comes with a low salary.

If you want to do better than that, you'll likely have to be a cofounder, not an employee. I read PG's essays in the early 00s, prior to the creation of YC, and his whole shtick was that ambitious employees can't hope to capture the value of their work, that sharp and hard-working tech folks should fund startups to truly capitalize on their efforts.