I’m currently living in Portugal and want to start a company for an app which I expect to have customers worldwide.

I know people can create a company in other countries to the one they currently live in order to get various benefits like lower tax. For example I’ve seen many posts about Delaware or Estonia. But what are the criteria for doing so generally? Do you need to have clients in that country, or do you need to be operating the business from that country (so I would need a cofounder is living in US for instance)?

And could Portugal have their own laws which need to be considered to with regards to this?