Can I access SNS (Portuguese public healthcare) on a residence permit?
Short answer: Yes — once you have a residence card plus NISS, you register at your local Centro de Saúde and get an SNS user number.
Until SNS enrolment, the consulate requires private health insurance covering you in Portugal for the duration of the visa. After arrival + AIMA + NISS, you can register at your Centro de Saúde and access SNS at the same cost as Portuguese citizens. See healthcare FAQ.