What would be the status of someone who's OPT has recently expired and is on his grace period? I am thinking of applying waivers for all i-821 fee, Biometrics fee, and i-765 fee? Is that a good idea? do you only need copy of passport and nepali citizenship besides all the forms?

I have heard if you apply for EAD through c19 category it is processed soon and you can get it faster. Is that so? What's the expected duration of receiving the EAD card under that category from the date of filing the application.

Thank you for you answers.

If you want to file the waiver form as well, then you will have to send some extra documents. I heard processing waiver can be pain in the ass and will just extend the time for tps to get approved. So it might not be worth it.
You will need copy of you passport, two photos, evidence for continuous residence.

Something like bank statement?

Bank statement will work to prove continuous residency. Other evidence can be phone bill, rent receipt. If you read the i821 form instruction, you can find bunch of documents that can be used as evidence.
Btw you will also have to send a photocopy of your current ead card.