I realized that when copying a page in webflow it is not possible to choose whether the CSS file that comes with it should be copied either or not.
The CSS file stays the same and is just referenced to the new page which should work fine for some users, but not all I guess. So in the end when you make changes on certain elements on the new page it affects the original page too which is not what you would usually want (for that purpose there are Symbols).
Using combo classes is what I tried already and it usually works kind of OK but just imagine if you want to change an element where you already applied two or three combo classes.
That is a mess and you loose all kind of order and overview, and just think about you copy a third page...
In my opinion it is absolutely not practical