Have at least 5 years of expenses in a taxable account. Have those funds in a combo of cash and the most tax efficient funds possible.
Then you take your 401k and turn it into rollover pre-tax Ira, and then put your lump sum pension in a pre-tax IRA. You start converting about 35000-40000 a year (or whatever you’re comfortable with based on your family subsidy cliff — see below) into a Roth IRA from your pre-tax IRAs. This will constitute your entire yearly income and keep you qualifying for ACA subsidies and maybe other things if you have dependents. In 5 years, all of this conversion is available to you without the 10% penalty and before age 59.5. This works best for those in a position to be retiring very early, but the principle holds as well for those just trying to get to 65 without outrageous ACA costs.
More info:
https://www.brandonrenfro.com/roth-conversion-ladder/
https://www.ehealthinsurance.com/resources/individual-and-family/who-is-affected-by-the-aca-subsidy-cliff
Enjoy.