The modern collection of interplanetary observatories allows for unprecedented multi-vantage point measurements of suprathermal to energetic particles, enabling systematic study of the longitudinal and radial variation in solar energetic particles (SEP) properties. Despite the observational progress, key characteristics such as the wide-spread nature of SEP events, radial variations in particle fluence and spectral profiles, and composition characteristics remain highly event-dependent and poorly constrained. This session invites contributions that address the fundamental physics governing particle access, transport, and variability within the inner heliosphere through both data analysis and modeling approaches. Topics of interest include (1) What are the dominant physical processes that govern the longitudinal extent of SEP events and (2) What are the fundamental drivers that establish and modify observed variations in SEP properties (e.g., spectra, composition, etc.)? We encourage contributions that take advantage of multi-point (real or synthetic) observations and that feature novel analysis techniques and approaches.