In Physique, by default, any number of overlapping envelopes can influence vertices. This is specified by the N Links option on the Vertex-Link Assignment rollout of the Physique Initialization dialog, or at the Vertex sub-object level.
Typically, N Links is the preferred choice. For special purposes, such as developing for a game engine that has limited support of overlap, you can limit the number of links (with their envelopes) that can affect a vertex.