I think VAT policy is the same all over EU so I think the same rules apply as here in Slovenia.
Actually having an VAT ID and have to charge VAT is not entirely voluntary. In Slovenia the limit of having to “enroll” into the VAT system was raised from 25.000 € to 50.000 € of annual revenue. So if during a calendar year you exceed this limit you HAVE to start charging VAT.
But you have to charge VAT only when you invoice in your country, if you invoice to another country (even within the EU) you do not add VAT to the invoice.
So being in the VAT system is actually beneficial if you for example make most of your money from Envato, because you essentially get any VAT you pay for services or products in your own country back.
Fo example if in slovenia I buy stuff or pay services for 500,00 € + 20% VAT = 600,00 €, and would make all my income from Envato, I would get those 100,00 € of VAT back from the government.
Furthermore if you have a valid VAT ID, even if you buy stuff from an other EU member country, where you pay their VAT, with the proper documents, you can even get that VAT back. Usually web stores and such require you to send some sort of documents to prove that you have a valid VAT ID.
But you have to check the rates and limits in your own country. I don’t know how it is in other EU countries but here if I would exceed the limit before voluntary enroll for an VAT ID there would all sorts of complications with the TAX monsters.