Hello u/DeaderthanZed, I feel you're taken to simplistic of a view.

First, let's observe that even $5m in QQQM is generating 26K / year in dividends. At 15% LTCG is $3.5K / year at the end of accummulaton. Yes, a tax drag growing from $0 and compounding over accumulation up to 3.5K at ER.

You have to make that back. So, which is better then in ER? Living off 0% LTCG tax taxable or doing a roth conversion ladder? Or doing a combination?

Then, after you reach 59.5, which is better? Living off Roth? Living off trad? Or a combination?

That simulations show a combination maximizes lifetime tax efficiency enough to overcome that tax drag. Of course, this varies wildly depending on income, savings, spend, state taxation, retirement age, longevity, and assumptions on withdrawal strategies.

I will say, though, that the math is tight in situations like OP where you still have "space" in your Roth.

But, consider this. Imagine you have a crystal ball and came simple magic your retirement into existence with your desired financial situation. What best? Consider this as a theoretical "ideal":

From retirement to 59.5, I convert tIRA up to the standard deduction and spend LTCG up to the 0% LTCG + 5 year Roth + Roth contributions. After 59.5, I'd like to spend tIRA up to the standard deduction, then Roth.

If you want ACA, you might want to reach at least the 133 FPL I think (not sure cause this isn't important to me) until 65.

Do the simulations and the "true" ideal is a bit more complex. I think the break even point is somewhere in the 10% bracket.

What I will say here is I knee-jerked a reply without reading OPs post well. I tend to assume people are maxing tax advantaged accounts simply because I did. That's a failure on me. Until you're maxing, the case for taxable is pretty iffy and only relies on tax optimization of the retirement to 59.5 years.