Thanks for the ping, Josiecat! I'm flattered that people think I know stuff about taxes.
My reply is going to match up with the others, but I'm going to focus on your question vs. theirs. (Their questions are good ones, BTW, but you don't owe me an answer on them.)
A pension cash out is, I'm fairly certain but not completely certain, treated as ordinary income, plus the 10% penalty if you're under 59.5.
Taxwise, the way it works is your pension cash out and Roth conversions are going to be stacked first, then your net capital gains from selling your investments stacks on top of those. Then your standard (or itemized) deduction gets removed from the bottom of the stack. Then the tax brackets are applied to what's left; first the ordinary brackets as applicable, then the capital gains brackets as applicable.
There are conditions and asterisks and stuff I'm leaving out of the previous paragraph, but that's enough to explain that your pension cash out will use up or fill in your standard deduction amount along with your Roth conversions, which is I think the question you were wondering about.
Collectively, the first $24.5K (or whatever) of your pension cash out and Roth conversions will be federally taxed at 0% due to the standard deduction. Anything above that amount will start filling the 10% bracket, which since it sounds like your MFJ is about $20K wide IIRC.
But you should also consider the impact(s) of the pension cash out and Roth conversions pushing capital gains out of the 0% bracket into the 15% bracket, and any ACA subsidies being reduced, as the other posters have said. (There can be similar effects with Social Security taxation, but that seems not to apply currently.) Increasing AGI also often has a state tax impact.
The order of the stacking of your pension cash out and Roth conversions doesn't matter. The 10% penalty would apply to the entire pension cash out amount because it was includable in income. You may want to check to see if you qualify for an exception to the 10% penalty by looking at the instructions for Form 5329 Line 2.