Mini-split HVAC in new build?

Next few weeks I will be in the process of getting quotes for mini-split HVAC system. Curious, if anyone has gone ductless and if so, how is that working out?

The house will be a a two story build(Buffalo area): main floor with an office and a living/dining/kitchen, and a 2nd floor with 4 bedrooms and 4 bathrooms. We will be insulating the foundation, the attic and spray foam the cavities. There will be two fireplaces(master bedroom and living room) that will be actively utilized during winter. All bathrooms will have heated floors and towel warmers.

By looking at the drawings It looks like 8 head mini-split should be sufficient to cover the whole area: 1 head x each bedroom(4), 1 head in the upper hall(cooling lower hall too), 1 cassette in the dining/living/kitchen area, 1 head in the office and 1 cassette in the basement.

Few areas of concern are:

Heating: Given that last few years have been somewhat cold in Buffalo, how good are heat pumps w/mini-slits at keeping the place warm? I’ve been reading that heat pumps may not be a way to go if outside temperatures are below -15c.

AC/cooling: What would be the best way to cool the bathrooms? Besides proper ventilation, cold air from the heads wont have direct way into the bathrooms so I am a bit concerned with not having a “sauna” during +35c days. I think an air handler or a ducted mini split zone may be a solution for the smaller spaces?

Electricity: how much would such system consume comparing to conventional forced air HVAC systems?

We’ll do a heat load calculation before going any further but I just wanted to get some head start and some input.