The Spanish constitution devolves a lot of power to these autonomous communities. All of them have the power to manage their own finances and they are all responsible for the administration of education, health and social services. They are also in charge of cultural & urban development.
This means that the laws and taxes in Spain can vary between the various autonomous communities.
Some communities have more devolved powers than others. In some the laws can be very different. In others there are special tax regimes. Some have their own police force and some have a second ‘official’ language.
As a result, you should take advice from a professional who is an expert about that community – and Law Overseas produces regional variations of its guides about Spain.