Curious why you think you'll ultimately be "happier" with the funds in the Roth. Are you expecting your marginal tax bracket to increase above 25% in the future (say, once you're required to start making RMDs)?
My feeling is that Roths are most useful for people who expect to have higher incomes during retirement than they had during their working years. When you contribute to a Roth, you are paying the taxes now in order to allow that money to grow tax free afterward. For someone who was in the 33% or greater tax bracket while working and who now has a large 401k that will have massive required distributions (in the 28% or greater tax bracket after age 70), filling the 25% tax bracket by making partial Roth conversions after FIRE makes sense, because they would be paying income tax at a lower tax rate for the conversions than they would have by contributing to a Roth while working (or than they would pay by waiting until after they begin RMDs). However, for someone who never exceeded the 25% tax bracket while working, filling the 25% marginal bracket makes much less sense, because now you cannot arbitrage your tax rates. Just another perspective to consider, especially since there's no pressing reason why you have to convert your entire tIRA within seven years given your relatively young age (say, rather than converting $10,000 per year for the next 15 years).
