You don’t need anything. You’re entering a Schengen area and you have a valid Schengen zone RP. It’s just like you’re entering Portugal. So, chill.

You don’t need anything else. Just your passport and Portuguese RP suffice. The Residence Permit of a Schengen country can be used to travel within the Schengen zone just like a Schengen visa. Not only that. It can also be used to travel to the non-Schengen EU countries like Cyprus, Romania, Bulgaria and also non-EU countries like Mexico, Colombia, Brazil, Turkey, Northern Iraq, a few South American countries, some GCC countries, etc.

Why aren’t you considering other options like Germany, Belgium, the Netherlands, Denmark, etc.? The pay will be much higher than in Portugal and Italy.