Comparison between the EWs of the metastable helium line and the helium C (a proxy for the expected helium S/N based on the model EW and the J-magnitude; Eq. (B.9)). We include the observed helium planet sample as compiled in Orell-Miquel et al. (2024), as well as potentially good targets that have not yet been observed and have helium C > 3 × 10⁻³ s^−1/2 cm⁻¹. For the observed planets, we plot observed EW values, while we plot model EW values for the planets that have not been targeted yet. They are also listed in Table B.1.