I plan to provide services (commercial and other) with drones ‘open’ category

You can operate your services whether commercial or not, under the 'open' category, if you meet all the requirements defined for the 'open' category.

See Question on subcategory under “understanding EU regulation 2019/947 and 2019/945”.

Regulatory reference: Article 4 of EU Regulation 2019/947; Annex part A and Article 5(1) of EU Regulation 2019/947.

The drone operator should develop procedures adapted to the type of operations and to the risks involved. Therefore, written procedures should not be necessary if the drone operator is also the remote pilot, or employs just one remote pilot. In this case the remote pilot may use the procedures defined by the manufacturer's manual. 

If a drone operator employs more than one remote pilot, the drone operator should: 

 (a) develop procedures for drone operations in order to coordinate the activities between its employees; and 
 (b) establish and maintain a list of their personnel and their assigned duties. 

Regulatory reference: UAS.OPEN.50 under annex part A 2019/947.