You are required to hold confidential stuff for life, like business contracts, but you can use your know-how, if it does not violate any patents, in a competing company as you see fit. This knowledge is a part of you and cannot hold you against employment. Even if you do decide within those two years to employ yourself in competing company, this can be held back by your original company only if they give you X% of your pay at them (X can be 80, or as low as 50, as my friends inform me).
Enforcement can maintain litigation longer than you can maintain solvency.
California bans anything that is effectively a non compete.
So the callout to be wary of them is totally legit... but it doesn't look like they are going to be enforceable when such things go through the courts.
Not sure how that's going.
"Defendant has never worked in any other industry. He has three kids. He's gotta work."
(That's for regular employees--it's a different issue with founders who may have significant equity stake and such.)
The worst is that they can delay the case for years, leaving you in a legal limbo. Or go after your employer, involving them in the discovery process.