If I need a business visa for Beijing, China, will I have to fill in the 2 forms: V2011.A and V2011.B and send online?

You don't need to fill in the form V.2011B if you apply for business visa in your home country.

If you are applying to work or study in China, or if someone else travelling with your shares the same passport, or if you are appluing for a visa in a country or terriorty other than the country of your current nationality, you should fill out the Supplementary Visa Application Form (Form V.2011B)

If you go to Copenhagen to submit visa application in person or entrust someone else to submit the application on your behalf, you don't need to send it by mail also signed.

If you want to apply visa by post, you need to send the form by mail also signed.