"as a stand alone form for 2021 to pay those 2021 penalties, and no need to amend the entire 2021 returns"

But it's more than Excess contribution penalty. You have taxable earnings. That's why I'm pretty sure you need to amend 2021. Well, unless the account lost value below basis as of Dec 31, 2021. And 2022 will have earnings (or loss), even if no penalty.