Insulated or Mixed Water Toilets?

We're building in upstate NY--cold area, hit -11º this winter and hot & humid summers are not uncommon. Framing is 2x6 with i-joists, we're still deciding on insulation, and HVAC will either be forced air or radiant with central air. We are taking great pains to build airtight, with gasketing and weather barrier on exterior.

We will use the house only a couple of nights per week, since we have to travel for work. Other days the house will be in some degree of setback mode. Our plumber has suggested certain upgrades, and feedback is appreciated on each of them:

We have selected the Toto Soiree WC for most of the baths, plus one or two Duravit wall-hung. Plumber has suggested putting two mixing valves to feed the toilets, which I assume means to mix some hot water into the cold--"to reduce condensation, since the tanks are not insulated." Is this a good solution?

I want thermo pipe insulation on the HW PEX supplies--he is suggesting Armaflex on both the hot and cold -- cold to be insulated against condensation. Supply lines will run through insulated floors, but otherwise, the house sits on an unheated 4' crawlspace. Is there a version of Pex that comes already jacketed/insulated?

What firestop, airstop or other material is best for sealing thru stud penetrations--particularly to keep the inspector happy?

Any other bits of wisdom that will help insure a top-notch installation?

Many thanks for all feedback, Mark

Condensation can be a problem, but isn't anywhere near as much as it was with the older, higher volume toilets. Modern toilets do NOT dump the entire tank, so unless you flush multiple times in a short period, there's some room-temperature water in the tank to temper the incoming. This may keep things above the dew point. An insulated tank may not solve this either, so, if you expect a problem, a tempering valve to mix hot and cold is a guaranteed solution to a problem you may not have. Keep in mind, insulation only slows the movement of heat, it doesn't stop it.

Properly sizing the HVAC system to allow it to keep the humidity levels comfortable, and running an exhaust fan when producing a lot of humidity (baths, showers, etc.) will help eliminate the problem.

Pex sweats much less than a naked copper pipe would, so other than for energy conservation, insulation may not buy you much there, either. Can't hurt, and is a good idea on hot, especially if you are doing recircuilation. If the pipes are in a closed, insulated space, there SHOULD be little excess moisture, so there shouldn't be much of any condensation anyways. If there are leaks because there's air inflitration, then there'd be moisture vapor available to condense, otherwise, it should be pretty dry.

Most of these toilets use only part of the water for the flush.
That being the case, with each flush you only add some water to the tank, unless you hold the handle and force it all out of the thank.

Your plumber can add mixing valves, though the hot after extend periods of time will cool down to house temperature.