Hard question to answer. But 7 tons for your sq footage sounds like a lot on the a/c side. 200k btus in furnaces - holy cow. I was thinking my father had an old house (1910) that had 100k btus on the lake in Wisconsin.....for 3000 sq feet. My seat of the pants estimate is that you would need 1/3 of what you were quoted.

Not another propane only heating system in the North!

So nothing about your system seems reasonable.

The standard here is manual J and post your electric rates. Geothermal is generally the only reasonable option if propane is your fuel (IMO).

what is your total cost for electric? I would say air-source heatpump at the very minimum. If you have a decent side yard go with geo-thermal if you can afford it. If electric rates are good you would have electric backup instead of propane. Propane is very expensive. Not worth it in my book unless you electric is nuts expensive. Even if you have expensive electric at the minimum you should have air-source heatpumps. They aren't that expensive to over a regular A/C and do a nice job heating above 30. They can go below also. These work great with nice well-insulated newer homes.

Thanks for your feedback. I missed to mention that we are planning on dual fuel. The cost of energy is 12 cents.
We don't think that geo-thermal is a good option due to the high upfront costs, since we may have to sell the house in five to seven years.
I have been learning about Manual J calculations and it looks like it's not a requirement in Connecticut - that's probably one reason why some HVAC contractors get away proposing oversized systems.

At 12 cents, I don't see the point of having propane but that is just me. You are about even on costs to heat with electric strip and propane at current prices.

I'd at least get some bids on geothermal. 30% tax credit goes a long way.

Building in the current market with a short term outlook makes little financial sense. Of course, buying a house with a short term outlook might not make sense either...

I'd do your own manual J just to get a rough idea. If you have your building plans, it is pretty easy since all the measurements are there. Still a few hours entering data but much easier than measuring every window and wall....

What is being proposed is grossly oversized. I am assuming your 2X6 construction will allow you to have at least R-19 insulation in the walls, and the Anderson windows are also a great help.

If I had to guess (and I do not recommend this), I would think two 2-ton air conditioners and two 60K furnances at 95% efficiency would be adequate. But please get a Manual J load calculation done even if you have to pay someone to do it. The dual fuel option makes sense if you are going to use propane.

definitely get heatpumps. The ones mentioned (14.5 seer models) are good. I wouldn't get any higher efficiency.
Does each floor have 2600 sq. feet? If its 2600 sq. feet total then 7 tons is WAY oversized. I wouldn't bother with the propane personally.

How tall are the ceilings? If you have tall ceilings I would say 5 tons max. Thats MAX. If you have new construction and its well insulated 4 tons would be just fine. Thats assuming you don't have vaulted ceilings, maybe just regular 9 foot. 4 or 4.5.