What must be decided regarding the facade before the shell construction?

You will have to assess that yourself

Can thin bricks keep up with the look of real clinker bricks?

Thin bricks are real clinker bricks, exactly the same stone - just thinner for bonding. There are functional differences but none in appearance. Problems with a late change of the facade mainly occur with windows and doors. The additional structure must be taken into account somewhere in the measurements.

Slips are real clinker bricks, exactly the same stone - just thinner for bonding. Functionally there are differences but not visually.

Basically yes, but there are often no slips of “nice” clinkers... What are the functional differences? Can it generally be said that the quality of real clinker masonry is significantly higher?

Does a facade not have to be visually approved? Before the building application or approval? I would say so.

Doesn't a facade need to be visually approved? Before the building application or approval? I would say so.

Not in our case.