On the deeply important :-) Visa/Not a Visa discussion, found this on the US's ESTA website...
WHAT IS THE DIFFERENCE BETWEEN AN ESTA AND A VISA?
An approved travel authorization is not a visa. It does not meet the legal or regulatory requirements to serve in lieu of a United States visa when a visa is required under United States law. Individuals who possess a valid visa will still be able to travel to the United States on that visa for the purpose for which it was issued. Individuals traveling on valid visas are not required to apply for a travel authorization.
https://esta.cbp.dhs.gov/
And this from the ETIAS FAQ's...
Is ETIAS travel authorisation equivalent to a residence permit or visa?
No. Having the travel authorisation only allows you to enter and remain on the territory of the European countries requiring ETIAS for a short-term stay.
Also, it does not give you the right to study long-term or to work in these countries. If you plan to stay in a European country requiring ETIAS for a longer period, you will most likely need a long-term visa.
Travellers with a valid visa do not need an ETIAS travel authorisation.
https://travel-europe.europa.eu/etias/faqs-etias_en