In this work we perform correlated structural and optical studies of single nanoparticles as well as explore the generality of SMSERS. First, wide-field plasmon resonance microscopy is used to simultaneously determine the LSPR spectra of multiple Ag nanoprisms, whose structure is determined using TEM. Next, the structure-property relationships for well-defined and easily-controlled nanoparticle structures (e.g. monomers, dimers, and trimers) are studied using correlated TEM, LSPR, and SERS measurements of individual SERS nanotags. We present the SER spectrum of reporter molecules on a single nanotag comprised of a Au trimer. It was determined that of 40 individual nanotags, just 19 exhibited SERS. The remaining nanoparticles were established by TEM to be monomers. These results demonstrate that SERS signal is observed from individual nanotags containing a junction or hot spot. Lastly, we explore crystal violet, a triphenyl methane dye that was used in the seminal SMSERS investigations, and re-examine single-molecule sensitivity using the isotopologue approach.