In what two plate tectonic settings do most volcanoes occur

The answer to your question is Divergent and Convergent

Divergent and convergent plate boundaries.

Explanation:

Most of the volcanic activities occur at divergent and convergent plate boundaries. Decompression melting at divergent plate boundaries leads to formation of magma. Convergent plate boundaries experience magma formation where water serves as flux and reduces the melting temperature of nearby mantle rock.