E6 Visa for ARI Biometrics

It is my understanding that portugal recently started to require those who do not have schengen-visa-free passports to apply for a E6 national visa in order to attend the ARI biometrics instead of normal tourist visa.

Does anyone have experience with the E6 visa? Does it still allow the holder to travel to other schengen countries (a) before entering portugal? and (b) after completing the biometrics? (whether for flight transit or just staying in another country before or after the appointment)

There seems to be very limited discussion online of the E6 visa when using it for AIMA purposes, hoping that someone has some insights! thxxx