The following Arnold settings are available for NURBS surfaces via the attribute editor:

NURBS Tesselation

MtoA relies on Maya to tesselate the NURBS before sending it to Arnold as a polymesh. MtoA does not support simple 'Simple Tesselation Options', however, it does support the 'Primary Tesselation Attributes' under 'Advanced Tesselation' (see images below):

_{Per Span # of Isoparms: UV 1 (left), UV 3 (center), UV 6 (right).}