If you set both "View" and "No self-service", such users will still see the "New" button but they can create Collection or Dashboard only in their own personal collections.
Users can always curate their personal collections, but if you think about it - they cannot do much if they were restricted from the day one. The only items they would see in their own collection is whatever some admin puts there. Otherwise, they are not able to move any of the saved questions or to create new ones.
Hence the term "No self service". They need to be "served".
IMPORTANT
Do not forget that Metabase permission model is additive! If user is a member of more than one group, the most permissive group setting will be applied.
In your scenario if GROUP1 has "View" and GROUP2 has "Curate" and a user belongs to both groups, they will be able to curate.