Due to their proximity, local star-forming galaxies (SFGs) are ideal for studying the physical properties, stellar population, and nebular gas in much more detail. However, the aperture size used in the optical can significantly affect the determination of the metallicities and physical properties of such galaxies. To study the impact of aperture effects, I will present the results of the analysis of local SFGs with optical spectra obtained using different aperture sizes. Such a sample belongs to the COS Legacy Spectroscopy SurveY (CLASSY), which comprises UV+optical spectra covering a broad range of physical properties. We calculated the physical conditions, metallicities, and star-formation rate. We found that the results of the electron density and temperature, and metallicities derived using longsilt, or IFU, are consistent but with slight variations in the extinction derived using the Balmer decrement. In addition, I will briefly present a preliminary analysis of photoionization modeling to simultaneously reproduce the low, intermediate, and high ionization nebular emission of CLASSY galaxies, taking into account some UV and optical observables. Then, the information obtained using UV+optical spectra allows constraining the nebular properties and young stellar population to model the emission line covering different ionization states of the gas. It will allow analyzing the processes required to interpret the high ionization features and the physical conditions at different redshifts.