Bricks: Are differences in the thermal conductivity value of 0.03 noticeable?

"My" house is as old as I am, monolithic aerated concrete caliber 300. You can bear it in every season. My annual statement says I’m usually around the average. Chill out, and under no circumstances plan your house with this focus. We don’t even have the partition walls made of sand-lime brick, and yet I don’t hear the dog next door (in case that would be your next worry after checking the thermal transmittance).

360 solid bricks from before WWII here. Our children also don’t have to freeze in winter; we have 20-22 degrees depending on the room. So don’t worry about staying warm, it will always be...

I would rather consider the storage as a "gimmick," even though I have one myself. I would definitely invest more in insulating the house. Maybe a few points can be found and boom, the insulation might even be paid off

Since an air-water heat pump is planned, the heating costs are included in the electricity bill. If I still have a storage tank, I wonder whether the higher heating costs could be reduced or even eliminated by the photovoltaic system?

360 full bricks from before WWII here.
Even our children don’t have to freeze in winter, we have 20-22 degrees here depending on the room.

So don’t worry about warming up, that will always happen...

That is very reassuring :) and you mean with my combination of air-to-water heat pump and underfloor heating, that should be more or less okay? Since money is already a Rolex for me, I want to implement the financial and felt, i.e. the really noticeable, measures as well as possible. And conversely, I want to postpone the non-noticeable ones to the end. My only concern is that I might do it exactly the other way around in some places and regret it afterwards.

One thing I have to say about this: The more thermally conductive the stone, the colder the exterior walls feel, even if the air temperature in the room is comfortable. I have the T10 myself, and when I sit on my daybed in the office to relax (but not sleep), I lean against the exterior wall, and these days that is no longer cozy, even though we have 21-22°C room temperature (possibly even more in the small office if I have spent the whole day there and the PC is running at full speed). Whether it would be noticeably better with the 7er, I cannot say...
Then why actually think so much about it:
With T10 walls, the insulation would have to be better elsewhere, because I only managed the Building Energy Act 2020, not KfW55, which is just above that. And your energy consultant has to calculate precisely, as in my opinion the component limit values are then exceeded there. Whether it still makes sense together from a calculation perspective, one has to figure out....

Since an LW heat pump is planned, the heating costs are on the electricity bill. If I also have a storage unit, I wonder whether the higher heating costs can be reduced or even eliminated by the photovoltaic system?

10kWp system: December 2023: production 125 kWh December 2022: production 155 kWh December 2021: production 152 kWh ==> If you have > 20 kWh consumption on cold days, you can calculate for yourself how sensible the storage unit is. August 2023: production 1,180 kWh August 2022: production 1,310 kWh August 2021: production 975 kWh ==> If you then keep in mind that you only produce hot water in summer, the storage unit doesn’t make sense for that either. Of course, storage units can be discussed. But not only in terms of heating. And you also have to take into account that both production via photovoltaic and usage via the battery cost money; you have to calculate carefully and it often turns out that a storage unit is not worthwhile.

And conversely, I want to push the imperceptible ones to the end. My only concern is that in some places I might do exactly the opposite and regret it afterward.

In this sense, I would actually push the stones to the back. Plan the house, the walls just frame the rooms.