Something to consider: depending on how much you spend each year maybe just keep the 400k in a HYSA/CDs. It’ll do a couple of things:
-allow you to be in a crazy low tax bracket during the first few years of retirement, giving you the opportunity to convert big chunks to Roth at a low tax rate.
-Give you the confidence to retire/stay retired if/when the market gets choppy. It’s easier to spend cash when the market is down than sell securities at depressed prices. A lot of people delay retirement, reduce spending, or take on paid work unnecessarily because they struggle drawing down on their portfolio when prices go down.
Ultimately whatever helps you feel confident in your plan is what you should do!