The paper presents a theoretical modeling of starburst galaxies using both PEGASE v2.0 and STARBURST99 codes to generate the spectral energy distribution (SED) of young star clusters. The models are compared using the MAPPINGS III code to compute photoionization models, which include a self-consistent treatment of dust physics and chemical depletion. The optical diagnostic diagrams, particularly the hardness of the EUV radiation field, are used to classify starburst galaxies. The study finds that warm infrared starburst galaxies contain a relatively hard EUV field in the 1-4 Rydberg region, which is attributed to the differences in stellar atmosphere models used for Wolf-Rayet (W-R) stars. The PEGASE models use Clegg & Middlemass (1987) planetary nebula nuclei (PNN) atmosphere models, while STARBURST99 uses Schmutz, Leitherer & Gruenwald (1992) Wolf-rayet atmosphere models. The inclusion of continuum metal opacities in the models may be a solution to the discrepancy between the observed and modeled EUV fields. The paper also discusses the role of supernova remnant (SNR) shock modeling and presents a new theoretical classification scheme for starbursts and AGN galaxies based on optical diagnostic diagrams.The paper presents a theoretical modeling of starburst galaxies using both PEGASE v2.0 and STARBURST99 codes to generate the spectral energy distribution (SED) of young star clusters. The models are compared using the MAPPINGS III code to compute photoionization models, which include a self-consistent treatment of dust physics and chemical depletion. The optical diagnostic diagrams, particularly the hardness of the EUV radiation field, are used to classify starburst galaxies. The study finds that warm infrared starburst galaxies contain a relatively hard EUV field in the 1-4 Rydberg region, which is attributed to the differences in stellar atmosphere models used for Wolf-Rayet (W-R) stars. The PEGASE models use Clegg & Middlemass (1987) planetary nebula nuclei (PNN) atmosphere models, while STARBURST99 uses Schmutz, Leitherer & Gruenwald (1992) Wolf-rayet atmosphere models. The inclusion of continuum metal opacities in the models may be a solution to the discrepancy between the observed and modeled EUV fields. The paper also discusses the role of supernova remnant (SNR) shock modeling and presents a new theoretical classification scheme for starbursts and AGN galaxies based on optical diagnostic diagrams.