Which masonry construction do you recommend for the exterior walls?

We had Liaplan stones built. They can be easily processed alone. The masons also told us that some people do this: have the first row set by the mason and then continue themselves. They are then only glued.

For own work, aerated concrete is actually the classic. It would also be compatible with calcium silicate bricks indoors. Poroton Dryfix could also be considered.

Basically, it doesn't matter whether it's aerated concrete or bricks. Both achieve the corresponding insulation values even without ETICS if you buy the appropriate thickness and the right type of brick. A Poroton T7 achieves Lambda 0.070 W/(mK), Ytong ThermUltra also achieves Lambda 0.070 W/(mK). And in the end, heat is lost anyway through windows and ventilation, so you don't need to overdo the insulation value on the wall.

I would always build only with aerated concrete + plaster, maybe next time with 42 or 49 cm instead of 36.5. But if the general contractor had taken bricks as T9 or T8, I wouldn’t have minded either.

An advantage of aerated concrete is also... when you drill, no red drilling dust comes out to dirty the nice white wall and fly around everywhere. A disadvantage of aerated concrete is definitely that you shouldn’t plan to hang heavy loads on the exterior walls. A 14 cm Tox anchor holds only about 40 kg in PP2 according to the data sheet. Or you glue in heavy-duty anchors directly.

ETICS achieves higher insulation values. But then you also have the disadvantage that anything heavier than a mailbox is hardly possible to attach sensibly.

And... own work? The shell? Have fun.

Oh, interior. Aerated concrete PP4 is okay, right? Most sound goes through the doors and, surprise, through the suspended ceiling. If you are already building with sand-lime bricks, then you need a reinforced concrete ceiling up to the roof and soundproof doors for the appropriate sound insulation.

The construction site has space for every brick.

Your preferred contractor often has his own system.

You misunderstood something. The OP does not want to be dictated the "that's how we always do it" approach, as it is about the most cost-effective and self-determined way, moreover he is probably better than a contractor and bricklayer through his self-study with the first house and also now by acquiring some knowledge, however that may be,

Which, in your opinion, is currently the most cost-effective wall construction according to the Energy Saving Ordinance standard?

Aerated concrete monolithic caliber 365, best processed by a single person.

We had a building made with Liaplan stones. They can be easily processed alone. The masons also told us that some do it this way: have the mason lay the first row and then continue yourself. They are then only glued.

First row and/or corners, there are different preferences. Aerated concrete is the lightest stone, therefore also good for large formats. If the stone is a bit heavier (Liaplan probably comparable in bulk density to pumice), it is also less beginner-friendly in handling: either each stone is heavier and therefore more strenuous to set and adjust at the same time and/or you need helpers or shifting devices, or each stone is not heavier (but then less large format). Both are equally bad, i.e. they reduce piecework performance. Whether you call the adhesive cream glue or mortar is more or less a matter of taste – either way, plan stones only allow 1 or 2 mm high bed joints, and the shear joints remain dry (here a toothed interlocking replaces the adhesive strength).

Porous bricks are even heavier = little beginner-friendly (which applies even more to filled versions) and unfilled ones are not a truly equivalent alternative.

If I were to build the walls myself, I would look at a Neopor ICF formwork system.

Beginners with at least some observer experience have no noticeable advantage from the even lighter insulation formwork stone compared to aerated concrete. One disadvantage is that you have to get somewhat familiar with the system. The basis here is not the octameter, but the decimal system with whole (5 cm) and half (2.5 cm) grid steps for cuts. Mixed with masonry formats, this can result in fiddling. Formwork "stones" were named that way for popular compatibility; they are even less stones in the true sense than aerated concrete, which at least is an artificial stone foam. The formwork stone only becomes wall material through its reinforced concrete filling. A delicate point is when the concrete mix delivered for processing by laypeople is too fluid (usually: with too much plasticizer) and especially if it is poured too high. On "Bauen jetzt" I wrote a post about this with the keyword "Bestgefahr" because then the "diaper" formwork stone has problems with it.