If you're over 59.5, paying taxes on Roth conversions with taxable savings (if available) instead of using pre-tax, deferred funds is generally the way to go. Since the limiting factor on conversion amounts is controlling annual income (and tax bracket), using taxable funds is functionally equivalent to moving the taxable savings used for paying the taxes into your Roth; i.e. you can move more into the Roth for the same tax bill. Funds moved into a Roth are available to someone over 59.5 anytime without penalty (provided they have a "seasoned" Roth over 5 years old), so there is no downside to the move.
The one potential issue is the capital gains status on the taxable funds used to pay the Roth conversion taxes. If the funds are invested with a lot of unrealized gains, you'll incur 15% CGT if your taxable income is over the top of the $78,750 zero CGT bracket (MFJ) for selling appreciated assets to pay the conversion tax. You'll have to work out how much, if any, CGT you might pay based on your specific circumstances.
For some circumstances, harvesting capital gains competes with Roth conversions for the best use of low tax bracket money.