The recent observation of GW190412, the first high-mass ratio binary black-hole (BBH) merger, by the LIGO-Virgo Collaboration (LVC) provides a unique opportunity to probe the impact of subdominant harmonics and precession effects encoded in a gravitational wave signal. We present refined estimates of source parameters for GW190412 using NRSur7dq4, a recently developed numerical relativity waveform surrogate model that includes all ℓ = 4 spin-weighted spherical harmonic modes as well as the full physical effects of precession. We compare our results with two different variants of phenomenological precessing BBH waveform models, IMRPhenomPv3HM and IMRPhenomXPHM, as well as to the LVC results. Our results are broadly in agreement with IMRPhenomXPHM results and the reported LVC analysis compiled with the SEOBNRv4PHM waveform model, but in tension with IMRPhenomPv3HM. Using the NRSur7dq4 model, we provide a tighter constraint on the mass-ratio (0.26+0.07-0.05) as compared to the LVC estimate of 0.28+0.13-0.07 (both reported as median values with 90% credible intervals). We infer the luminosity distance to be ~4% larger than the estimated values with phenomenological models and the quoted LVC result, constrain the binary to be more face-on, and find a broader posterior for the spin precession parameter. We further find that even though ℓ = 4 harmonic modes have negligible signal-to-noise ratio, omission of these modes will influence the estimated posterior distribution of several source parameters including chirp mass, effective inspiral spin, luminosity distance, and inclination. We also find that commonly used model approximations, such as neglecting the asymmetric modes (which are generically excited during precession), have negligible impact on parameter recovery for moderate SNR-events similar to GW190412. We further explore other available surrogate waveform models including NRSurHyb3dq8 for their routine use in parameter inference with current and future gravitational waves events.