Land Planning: 2 Single-family houses on a 1,200 m² corner plot

I would make it a duplex with 2 parking spaces/D-garage or carport combination on the left and right.
Houses touching on the short side.

Are the garages really not allowed to be built as boundary development? Then you could place them in the middle and build both houses more or less symmetrically, equally on the left and right. With a green roof on the garages, the rather ugly area can also be spruced up a bit from the perspective of the 1st upper floor and create a bit of a roof garden feeling (depending on how the lines of sight between the two houses should/may be).

Very valid suggestions. We want to build the houses staggered for the following reasons:

[*]To the southeast, there is a nice view
[*]We want the houses to stand somewhat at an angle so that both look out onto the garden in the south corner
[*]We do not want the terraces to be so close to each other

Is there a valid development plan?

No, like neighboring buildings. And we see quite good chances of approval for both options.

if there are any rules of thumb or how a developer would plan:

We want to build the houses staggered for the following reasons:

I don't understand your input.
Why do you ask how a developer would build and then 3 minutes later give an explanation why and how you want to build your way.
If you want to build, then with the optimum according to how you imagine living yourself, whether with a double garage or additional parking spaces, whether a courtyard adds value to you or not. That's up to you. And I wouldn't care at all how a developer, who doesn't move into the houses themselves, would build.

how a developer would plan:

As long as it fits into the 34er, he will build two semi-detached houses to maximize his profit. Leaving that much land unused as a garden is out of the question for a developer.

I don’t understand your input. Why do you ask how a developer would build and then 3 minutes later give an explanation of why and how you want to build this way? If you want to build, then with the optimum way you imagine living yourself, whether with a double garage or additional parking spaces, whether a courtyard adds value for you or not. That’s up to you. And I wouldn’t care at all how a developer, who does not move into the houses themselves, would build.

As long as it fits the 34er, he will build two semi-detached houses to maximize his profit. Leaving so much land unused as garden is out of the question for a developer.

I am not concerned with building like a developer, but rather understanding how the houses would have been arranged if one wants to appeal to as many potential users as possible. And then I can compare that with my proposals and see how I can justify the differences. Maybe I am overlooking something. Things like placing the garage far enough back to also be able to park in front of the garage, etc.

I would divide the plot in the middle. Then build a duplex.