Is the manufacturer of a product obliged to draw up a "declaration of conformity" and should you provide it to the customer?
Which guidelines apply to a product with electronics and powered from 230VAC?
The Declaration of Conformity must be provided with the products you mentioned. Not only on request, no you are required to provide as well as a user manual.
In the case of small parts, the information is printed on the packaging. This is an acceptable alternative for a attached statement. The Low Voltage Directive and the EMC Directive, I think, apply. Further, there may be other guidelines that should be taken into account, such as the ATEX Directive, the Machinery Directive, etc. This depends on the specific application of a product.