John, if you have to worry about estate taxes, you really need a tax attorney and accountant.
https://elder-law.com/estate-and-gift-tax-thresholds-set-increase-2018/
It will come as a surprise to some, for our situation, where we live in NY is the best option. Yeah, NY is supposedly a high tax state, but they treat retirees reasonably well. Any government pension, SS, Fed pension, NY state pension is tax free. In addition $20,000 of other retirement income (IRA distributions) is also tax free. Where we live, an older suburb near Syracuse the houses are modest and the property taxes low. If the retiree's income is below ~$86,000 there is a discount on the school taxes. Living expenses are also very modest.
If we were to move to a low tax southern state we might save on taxes but we would be forced to buy property (or rent) that would raise our monthly expenses. We're not willing to do that. Also, our boating expenses are very low. We have a nice dock in a good marina that is very affordable. Our annual expenses for dock, haul out, and winter storage is less than the summer dock fees at Buffalo area marinas.
The downside is the summer season is short and winter is snowy. But if you don't have to go to work the snow is not a big deal.