The "e" in eResidency does a lot of work. The scheme will not give you any residency rights or obligations in the physical sense. Just forming and running a company in the EU, including tax and banking systems that are aware of your non-resident status and making running a company easier.

As others have said, it mostly makes sense for people outside of the EU. If you have personal residency in Spain then it is questionable whether the easier paperwork in Estonia will offset the need to do some paperwork in Spain as well.