You can access ecoinvent online, if you never accessed before read here. Here you can look for the activities of your concern and see all the relevant documentation and flows in the undefined (i.e. before linking and allocation) and in the three system models form. Here you can also download the PDF documentation.
For more information on markets, I would like to refer you to the explanation of market activities on our website.
For it to be clearer for your study, you can for example download the PDF documentation for the GLO market for copper and consult the list of activities contributing to it. There you will see the mix of countries including Europe, which feed into the market. You can therefore use, for example, the GLO market for copper but use European activities for the assembly of the product.
Auxilliary and energy inputs are datasets that include the materials, energy and emissions related to the use of a machine (see the comment for the included activities in the datasets of your interest). In terms of the appropriateness of using datasets referring to other products, such as capacitors, we cannot really help you and you would need to refer to literature and experts in the field. In the end the modelling choices are a user’s responsibility.
To know more on how to use services related to working of metals, please refer to the previous answer of my colleague Emilia on the topic.
Lucia Valsasina, Data Analyst, ecoinvent