A. Here is the conventional wisdom when it comes to taking money out of the various investment accounts - start with your taxable accounts first, particularly if your income is low as you start your retirement and become qualifying for tax-free capital gains.
Next, you can take withdrawals from your tax-deferred accounts, followed by your tax-free Roth IRA accounts so you can take advantage of the tax-deferred and tax-free growth.
Exceptions to the Conventional Wisdom
If you have a large balance in 401K or Traditional IRA, your RMDs could push you to higher tax bracket, to avoid this, consider taking withdrawals from your tax-deferred accounts before age 70.5, but be careful in this strategy and not to push you into higher tax brackets in these years.
You can also consider converting some of the 401k or traditional IRA money to Roth IRA, but again you need to pay attention to the amount of the conversion so not get pushed into higher tax brackets.