Good questions, Marco!

As you suggested, only Publish elements that will be used as linked geometry in other parts and products.

This includes:

Geometric features (points, centerlines, planes, surfaces,etc) that will drive other features in other parts (External References with links).

Geometric features (axis, centerlines, faces, planes) that will be used in assembly constraints.

(I can't think of an example of publishing the entire CATPart (can you do that?), but I often publish a PartBody that I will copy&paste with link)

It is a good practice to name all publications, instead of using the default CATIA names (ie: "pivot axis" instead of "line.3")

In most cases; changes to sketches shouldn't make constaints go bad as long as you just modify existing geometry. But if you add new geometry, make sure you update the publication as well!