Wall structure in bathroom

Hello everyone, two questions about the wall structure in the bathroom.

1. Do I always need a preliminary wall behind the toilet / sink / shower? If yes, how should it be constructed, drywall or masonry (brick)?

2. In the second bathroom, we have an arrangement like a "T" with two sinks attached and a toilet and shower adjacent to each? Again, the question is drywall or masonry?

I hope you can give me some tips with pros and cons.

Thank you very much.

A porch was necessary for us because the toilet is located on the outer wall and no pipes are allowed to run there due to frost protection. If T solution for the washbasin, please do masonry; with drywall construction, you have to install a support plate.

ok thanks for the answer, for us it is a load-bearing interior wall where the WC is supposed to go... is that possible or only with a frame?

What would be the disadvantage of a mounting plate, it should work without any problems, right?

Does no one have an opinion on this yet, I would be grateful. Regards

Walls nowadays receive a cladding, a so-called [Vorwandinstallation]. However, installations can also run inside the wall. Masonry or drywall does not matter in this case. For [T] I don't know.

A toilet needs a flushing cistern, which is integrated into the cladding.