Peptide polymer amphiphiles (PPAs) are highly tunable hybrid materials that achieve complex, protein-like assembly landscapes by combining sequence-dependent properties of peptides with structural diversity of polymers. Despite their promise as functional biomimetic materials, determining how polymer and peptide properties simultaneously affect PPA self-assembly remains challenging. We herein present a systematic study of critical components within the PPA design space that dictate the self-assembled morphologies. PPAs containing hydrophobic oligo(ethyl acrylate) were used to interrogate the role of polymer molecular weight and dispersity in addition to peptide length and charge density on self-assembly. We observed that PPAs predominantly formed spherical particles (micelles and vesicles), with both polymer molecular weight and peptide hydrophilicity determining morphology. Additionally, peptide charge and polymer dispersity influence particle size. These key benchmarks will facilitate the rational design of PPAs that expand the scope of biomimetic and biocompatible functionality within assembled soft materials.