Are you sure you are talking about the Netherlands? Heating pipes routed outside walls I have seen in the UK, but never in the Netherlands. No soundproofing would NEVER pass building regulations in the Netherlands.
In my experience, water pipes (not sure about heating) routed outside the walls are pretty common in houses in Amsterdam build pre ~2000 (and not renovated since)
Depends on who did some renovation. Heating is usually routed trough the floor. Water sometimes in or against the wall, sometimes in the floor, and sometimes in sight, but never outside... In the past gas was routed out of sight as well, but that's not allowed anymore, so you see gas pipes usually in the corner of a ceiling. You can hide this with a facade.
Walls here are made from brick. The newer buildings are either normal or aerated concrete, and sometimes split up using drywall. This totally depends what the requirements are, and the past years, construction has been more and more drywall instead of brick etc. I've never seen a single layer of drywall, and I've lived in all type of housing in Amsterdam.
