@bmwermuth - it appears you got a lot of clarity from all the comments
1) none of the proposed regulations (which we might as well assume are the final regulations to be conservative) impact the year of death RMD. There was a 2021 requirement in your situation that could have been satisifed (and maybe was satisifed) by the other 3 beneficiaires
2) for 2022, the 4 beneficiaries are each on their own. Based on the new regulations each has an RMD requirment each year and the IRA must be liquidated no later than Dec 31, 2031. 2022 would be the first of those 10 years.
3) Since your wife was 64 in 2021, and assuming she turned 65 in 2022, her 2022 RMD obligation would be the December 31, 2021 balance of HER inherited IRA divided by 22.9. See page 49
https://www.irs.gov/pub/irs-pdf/p590b.pdf
4) in 2023, the RMD is based on the Dec 31, 2022 balance divided by 21.9. Then in 2024, it's the Dec 31, 2023 balance divided by 20,9. The divisor is reduced by 1 each year.
5) Those are simply the mimimums. What you don't want is to end up in year 10 with a large balance that has to be distribited; that may impact your tax bracket and even the IRMAA medicare premiums. So a thoughtful approach such as 1/10 of the balance the first year, 1/9 the second year, 1/8 the third year, etc, might be better than the minimum requirement. it'll take some assessment and maybe the use of a financial planner to limit any potential year 10 issue.
