Would mi amigos be nostros or ustedes.

Answer 1

It would actually be ellos or ellas because Ustedes implies that you are formal with your friends when your arent you are informal

Answer 2

Now if y ou are speaking to them: Mis amigos,......ustedes. Unless you are in Spain and where castellano is spoken, then it's vosotros/vosotras.

If you are part of the group = nosotros/nosotras but if you are not included in the group = ustedes.

Sra