The articles of association (Icelandic: samþykktir) can be described as a very basic version of the shareholders’ agreement, including some formalities regarding share capital, company name etc. They can also contain pre-emption right and post-sale purchase right.
The articles always apply to all shareholders in the company, no matter if they like them or not. Therefore, keep them very basic and put everything else in the shareholders’ agreement. To change the articles, you need a qualified majority at a general meeting. Just make sure that the articles are clean, and you will not have to update them frequently.