Fisher-matrix forecasts are presented for the cosmological surveys of the Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS) and the Subaru Prime Focus Spectrograph (PFS). The wide, low-redshift coverage of J-PAS and the high-density, high-redshift mapping of PFS are strongly complementary: combining the two reduces marginalized uncertainties on all primary parameters compared with either survey individually. Adding the joint J-PAS+PFS data to next-generation cosmic microwave background (CMB) measurements from the Simons Observatory and LiteBIRD yields an expected precision of σ(∑mν) = 0.017 eV in the ΛCDM+∑mν + Neff framework, sufficient to disfavor the inverted neutrino hierarchy at 2.34σ if the true mass sum equals the normal-ordering minimum. Motivated by recent DESI results, we also forecast within a w0waCDM+∑mν + Neff cosmology, adopting the DESI DR2 best-fit values (w0 = −0.758, wa = −0.82) as fiducial. The combination CMB+J-PAS+PFS then delivers σ(w0) = 0.044 and σ(wa) = 0.18, corresponding to a 5.1σ preference for a time-varying dark-energy equation of state. These findings show that J-PAS and PFS, especially when coupled with Stage IV CMB observations, will provide competitive tests of neutrino physics and the dynamics of cosmic acceleration.