Thank you for your advice.

I fixed the federal option to 2=Lesser of 90% of 2021 or 100/110% of 2020 tax and if fixed!!! 

Yes, I'm quite certain my client would not need estimated tax payment because he set much higher withholding amount from his W2 this year.

May I ask what is the right option for CA?

And what is "the ol' trusted prior year exception"?