re: Question about a pension plan and income during retirement

Yes you will pay taxes on the withdrawals from a tax deferred retirement accounts at your then current marginal tax rate.

It is always good to have both tax free, like a ROTH, as well as taxable money (IRA, 401k, 403b, etc) that can be used during retirement. Additionally, you should have after-tax investments which can be sold and withdrawn only owing the tax on gains at capital gains rate(this will probably rise in Biden tenure).
Tax brackets are fluid, depending on Congress' whims and the US economy. Tax rates will probably be raised, at least for the next two years, but typically cycle up and down.
If you have all three types of money you can supplement your retirement pension income most effectively by blending your account withdrawals to get he most after tax income based on that year's tax brackets. In other words, make decisions each year based on need, marginal tax brackets and rates, so that you take the maximum amount needed to satisfy spending needs while remaining in the lowest bracket. While tax rates are tiered, you still would do better if you plan carefully and avoid putting yourself into a higher bracket.
Knowing that brackets will probably come down, and rates go up in Biden-Harris times, 2020 was the time (if you were already retired) to take extra money out of taxable accounts (tax-deferred or after tax)and stockpile it to save tax payments in future years.