Right now I'm trying to figure out the ARP rule that limits ACA premium payments to 8.5% of income for this year and 2022. If it's really that straight forward, I'll be evaluating the value of a ROTH conversion versus taking LTCGs in my after-tax account.
Check out healthsherpa.com or healthcare.gov to run some scenarios on how this would work for you. Of course it works on this year's plans but at least you get an idea. Just realize that next year could be a lot different. The key to the subsidy is that 2nd lowest cost silver plan, even if you go for a gold or bronze plan.
Roth conversion for LTCGs. I assume you're talking about being able to take LTCGs at 0%? If not, I would probably favor conversions, but it's not a slam dunk.
First factor is, do you need more money for living expenses? That clearly favors taking LTCGs. You sell the stocks/funds, and put the proceeds in your checking account, and you only pay tax on the gains. Roth conversions are for future use. Otherwise you might as well just do tIRA withdrawals.
Second factor, what are your future tax rates? If you're going to pay 15% LTCGs whether you take them now or later, and you can convert at a lower rate now than you expect later, the advantage goes to doing Roth conversions. But if you can take LTCGs at 0% now and they would be 15% later, it might be hard to see a similar % rate difference in Roth conversions now vs RMDs later.
Third factor, what about heirs? Under current law, they would get stepped up basis on taxable holding, and would have to fully withdraw from an inherited IRA in 10 years. If your LTCGs are taxed, this clearly favors Roth conversion. If you can get 0% tax on LTCGs, it depends on your current tax rate vs theirs over the next 10 years. Look at what happens if you do one or the other now, and die next year. If you do a conversion, your heir pays no taxes on that converted money, and they can even keep it in a Roth for 10 years. But if you pay more taxes on the conversion than they would on a withdrawal, you shouldn't have converted. If you take LTCGs and paid taxes on them, it doesn't work out because your heir would've got stepped up basis and could sell on inheritance with 0 taxes.
So, not a simple answer, and probably other factors I didn't cover. Plus, those tax laws could very easily change. If stepped up basis goes away, that's a big game-changer.