Choosing the wrong hexes.

[Order of Chaos]

Each witch archetype has following sentence written in it "The following witch hexes complement the X archetype"

Are they compulsory?

Can witch choose different hexes and still have all of the archetype features available? (I am concerned the mostly about the Grand Hex)

Will witch's patron get mad at him/her for choosing hex that doesn't belong to certain archetype, given how patrons and archetypes are completely separate things?

For what purpose is it written there then?

[Duiker]

Yes, unless the archetype says that they cannot pick a certain hex (or has hexes removed entirely of course) you can choose from any of them. The text is there to give you ideas and hint at themes. Just because it doesn't do anything mechanically doesn't mean that it's worthless.

[Gisher]

They are not compulsory. They are suggestions.

[Cavall]

At most it's just thematic. At worst it's just flavor filler.

No obligation.