Total [O III]/[C II] line luminosity ratio as a function of SFR for the High-z model (red) and Schimek et al. (2024a,b) (purple). The top panel reports the comparison with observational data from Hashimoto et al. (2019) at z ∼ 7, Witstok et al. (2022) at z = 6.7 − 7, Carniani et al. (2020) at z ∼ 6 − 9, missing [C II] flux corrected values from Carniani et al. (2020) (SBD corr.) at z ∼ 6 − 9, Harikane et al. (2020) at z ∼ 6, Ren et al. (2023) at z = 7.2, Algera et al. (2024) at z = 7.3, Bakx et al. (2020) at z = 8.31, Laporte et al. (2017) at z = 8.3, Fujimoto et al. (2024) at z = 8.5 (lower limit), and Schouws et al. (2025a,b) at z = 14.2 (lower limit). The relations included are the z = 6 − 9 relation from Harikane et al. (2020), the best-fit relation from Pallottini et al. (2022), and the high-redshift, local dwarfs, and local starbursts (SBs) relations from De Looze et al. (2014). The bottom panel reports the comparison with simulation studies by Katz et al. (2022) (z = 6), Ramos Padilla et al. (2023) (z = 6), Pallottini et al. (2022) (z = 7.7), and Lupi et al. (2020) (z = 6). The relations are from Arata et al. (2020) (z = 6 − 9) and Olsen et al. (2017) (z ≃ 6).