Each and every country of the EU will have passed a law stating that EU regulations take effect in that country. Already existing legislation has to be changed in accordance with any new regulation and consequent legislation has to be in accordance with regulations. But, yes, regulations may also be implemented as administrative acts.

Van Gend en Loos gives EU regulation direct effect. In that individuals can enforce regulations in national court, thereby forcing a change of existing national legislation or administrative acts arising from national legislation.

Yes, I ment fines in an administrative and not criminal sense. But even though the EU sets the fines, in most cases, such as the GDPR fines, they still have to be collected nationally. So therefore necessary national legislation or administrative acts have to be passed.