Trying to sort this out is a complicated PITA. I bought a copy of Pralana Gold (a commercial spreadsheet app) to model my situation. It is a powerful tool for Roth conversion analysis but my head is still spinning. Trying to factor in the likely tax implications for inheriting kids takes it up another notch. Ultimately, I say screw em - they will get plenty. If I leave a few bucks on the table it will help the budget deficit.
I used Bigfoot's Retiree Portfolio Model over at BH several years ago to corroborate my gut conversion strategy back in 2013 that conversions up to the top of 24% bracket made sense for us. I'm not looking for mathematical precision in arriving at optimal conversions for us. So, just looking over my recent tax filing I probably had around $10K more of conversion space in the 24% tax bracket -- always difficult to be precise about this when you're considering IRMAA since IRMAA looks backward at MAGI two years ago, which as I understand from some of your prior posts you don't have to worry about.
My heirs are already in or beyond the 24% bracket on their returns and I expect, given their own financial trends, they'll likely wind up in the highest brackets in a few years from now -- so there's that too.
My CSRS pension takes care of all living expenses, including Federal tax withholding on my conversions. I pay no state taxes on my conversions using my TSP in NC where we live, so this has made me gradually rollover funds from my 401K to TSP and then rollout funds from TSP to a Roth IRA (once in Wells Fargo and now in Fidelity because Wells Fargo screwed up conversions I made in 2021 from TSP).
I'm keeping some funds in my TDAs for charitable donations or long term care expenses, though, like you, I have Federal LTCi.
We completed converting all of my wife's TDAs to her Roth IRA in 2020. And I began the process in 2020, and will likely have most of my funds in TSP as opposed to my Roth IRA.
I'm grateful that Secure 2.0 gave me an additional year before RMDs kick in for me as well as removing the RMD requirement for Roth TSP or Roth 401 funds, of which I do have a small portion.
I'm not a spreadsheet guy so I don't try to precisely calculate everything; I just need to be accurate in the landing zone. Good luck with modeling your situation.