Cold roof - house from 1995

We have just bought and moved into a house built in 1995. The attic is constructed as a cold roof, with DRAGOFOL as the underlay membranes on the slopes. The ceiling of the attic has the classic structure (from bottom to top):

- Gypsum plasterboard
- Battens (or maybe none? I haven't looked deeper yet ..)
- Beams, between them stone wool or glass wool (I have no idea)
- On top battens with a gap (this probably serves for ventilation as I have learned here in the forum)

Back then, apparently, no windproof diffusion foil was installed, at least I haven't seen any ..

Now I want to lay empty conduits to distribute LAN from the basement up to the attic. Before I run ugly cable ducts through the rooms .. I would rather run empty conduits over the cold roof.

What do I have to consider?
Do the empty conduits have to be under the insulation, directly on the gypsum plasterboard?

How much does it help to make the attic ceiling windproof with windproof diffusion foil?