Drywall for heavy washbasin

With me, we chose variant 3. A piece of plank between the drywall profiles in the area where the cabinet is attached.

Regarding insulation the following:
We don't have any behind it. For us, it is also a kind of shaft from the utility room below to the attic. All the cables go up into the upper floor ceiling and the ventilation ducts for the upper floor. However, we currently still have a problem with the acoustics in the bathroom.
It echoes a lot. It could be that it would have been better with insulation behind the drywall. I would therefore recommend that you research this further or ask professionals.

We are now trying to manage it with bathroom rugs and a pleated blind.

We chose option 3. A piece of plank between the drywall profiles in the area where the cabinet is attached

Thank you very much for your feedback. And was your washbasin + sink comparable in weight to ours (approx. 80 kg)?

Also thank you for the tip about the insulation. In this case, I will definitely install some - it’s not expensive.

Don't know how heavy it is now but it is a Villeroy & Boch Legato in 1.6m width and on it 2x Villeroy & Boch Subway 2.0 sinks.

It is 80 kg distributed over 6 screws, these are shear forces and not tensile forces, don’t worry it will hold.

@denz if there is a towel hanging and bath mats lying around, it changes immediately. It was the same for us at the beginning.

Thank you very much for your answers/help. Did I mention that I want to install a 50mm drywall - is that enough or do I need a 75mm or 100mm?