So far this has been the best calculator I've found. https://www.calcxml.com/do/ret10 But I cannot factor in the "gap" between retirement and withdrawal.

Option 2 seems like the most correct option to use. Big assumption we are going to add in the $8000 tax savings back into the account as after tax savings. If you are thinking about comparing $24,000 in Roth and $24000 in 401k with no after tax, then there is no real comparison. They will grow the same rate but you did nothing with the money saved from taxes.

But assuming we do everything correctly. Ie, save the max, it looks like the roth makes sense as long as you can afford the extra tax to max out the 24000 (catch up). Even if you are 55 and plan to withdraw starting at 60. I just want to make sure I'm calculating the numbers correctly.

If you assume the tax rates stay the same (all we can plan for), then anyone with 25 years here will be in the 28% bracket best case. We are not going to get a big windfall in tax saving after we retire. The Roth will allow some flexibility in not having mandatory withdrawal and we can always draw first from our previously accumulated 401k. I don't see the advantage of converting, unless I have lots of time left here, which I don't.