Hi Pilou - what you show there are examples of what you want to avoid doing.

Like this result:



That comes from applying sub-d smoothing onto a control cage that has not been set up for subd modeling, it's just triangles.

The result will be extremely overly dense and will likely contain a lot of bumps and undulations in it.

It will be difficult to use something that messy to do further work on.

So I'd recommend not doing any of what you show there, sorry!

- Michael