There is also a 10% early withdrawal penalty unless you are 55 and have separated from service. Withdrawals can begin after retirement at age 55 from the 401K (probably the 72t rule). Direct rollover to a rollover IRA, at any age after retirement, has no consequences because you are just transferring the money.
Your tax bracket is what you need to pay attention to like CharlieHustle said.
Dave - This is how people do Roth conversions - they withdraw just enough to keep them in the same tax bracket and convert that money to a Roth IRA. You will have to pay the tax at the time of conversion though. You can play around with a tax simulator to figure it out
https://turbotax.intuit.com/tax-tools/calculators/taxcaster/
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