Assuming your wife's parents died after Secure Act passed in 2019...
You have 10 years to take funds out in their entirety. It doesn't matter if you take them all in one year or spread over 10, they have to be liquidated within 10 years.
As said above, unless the 401k had Roth component, liquidated funds will be taxable as ordinary income. As a general rule of thumb, funds in Roth accounts can be invested for the full ten years, then liquidated tax free at max accumulation. Non-Roth funds can only be managed out to "fill up" your current tax bracket. Keep in mind that tax rates go up in 2026, so it may be advantageous to take funds over next two years.
There is likely a mandatory withholding of 20% from inherited 401k, thus the reason for rolling into an inherited IRA.
There was never an option for a non-spouse to roll into an IRA owned by said non-spouse, but you can match your distributions up with contributions each year to minimize tax impact. For example, take out $7000 from inherited account (taxable) make contribution to tax-deductible IRA. This can be done for both spouses to maximize impact, but you must have EARNED income equal to or exceeding the amount of IRA contributions, i.e. you can't be already retired for this to work.
Any further advice would be worthless without knowing your current income/income sources, current tax bracket, age, size of the inherited account, etc. You didn't mention it specifically, but FAFSA considerations if you have college age, or near college age children, are huge. There are a few strategies to be implemented, but those are limited after the death of the account owner.
Ridin' 'cross the desert. . .