But with that plan won't you get slaughtered with taxes when RMDs start?

The benefit of compounding of retirement accounts is popular misconception.

For example, let's say that you have $100,000 in a tIRA and $22,000 in taxable.

One option is to do a $100,000 Roth conversion and use the $22,000 in taxable to pay the tax. Let's say that the $100,000 grows at 7% annually... in 10 years you have $196,715 that can be withdrawn tax free. [$196,715 = $100,000 *(1+7%)^10]

The other option is to let both accounts ride. After 10 years the tIRA grows to $196,715 and when withdrawn results in a tax of $43,277 at 22%. Meanwhile, the $22,000 in taxable grows to $37,437 so you only have $190,875 to spend. [$37,437 = $22,000*(1+7%*(1-22%))^10]

The difference is that the growth of the $22,000 in taxable gets taxed over the 10 years so it doesn't grow as much.

Even if the growth of the $22,000 was tax free, is would grow to $43,277 [$22,000*(1+7%)^10] and you would have $196,715 after paying taxes.

So that proves that the benefit of compounding of retirement accounts is a popular misconception. Compounding provides no benefit. The benefit of tax-deferred accounts comes solely from the difference in effective tax rates when contributed vs when withdrawn.