I’ve just realized that in some countries in the EU you have to opt in to be able to donate organs in case of death. In others it’s the default and they offer opting out.

I see that as an automatic opt in from my POV.

Are there any other such simple things we should be opting in for in Romania, or the EU in general?

I’ll start: If you’re Romanian you should choose an ONG to redirect 3.5% of your tax to, otherwise it goes to the semi-corrupt government.