I'm already gifting to my beneficiaries up to the gift allowance ($19k each this year) that doesn't impact my lifetime allowance and need me to file IRS forms. QCDs have crossed my mind, but many of the charities I give to don't qualify as they are overseas. I have thought about giving through a Donor Advised Fund, but the amounts don't make it sensible.
I looked back at my ROTH solo 401k that I set up when I was doing some part time consulting and in the early years I was just in the 33% marginal tax bracket, but that fell to 24% in 2018 so doing conversions at the 24% level now that my part time work is coming to an end seems sensible.
The tax that my beneficiaries will pay overseas is an important consideration, but also is the possibility that I might move to join them in that high income tax country. At least I will avoid the 5% state tax if that happens and I'll get 4 year's in that country where I will be able to make conversions without having to pay the local tax rates on foreign sourced income so I might be filling the 32% bucket at that point...OMG!

I think I need to get married in this situation.