  Using 190,000 spectra from the seventeenth data release of the Sloan Digital
Sky Survey, we investigate the ultraviolet emission line properties in z=2
quasars. Specifically, we quantify how the shape of CIV 1549A and the
equivalent width (EW) of HeII 1640A depend on the black hole mass and Eddington
ratio inferred from MgII 2800A. Above L/L_Edd>0.2, there is a strong mass
dependence in both CIV blueshift and HeII EW. Large CIV blueshifts are observed
only in regions with both high mass and high accretion rate. Including X-ray
measurements for a subsample of 5,000 objects, we interpret our observations in
the context of AGN accretion and outflow mechanisms. The observed trends in
HeII and 2 keV strength are broadly consistent with theoretical QSOSED models
of AGN spectral energy distributions (SEDs) for low spin black holes, where the
ionizing SED depends on the accretion disc temperature and the strength of the
soft excess. High spin models are not consistent with observations, suggesting
SDSS quasars at z=2 may in general have low spins. We find a dramatic switch in
behaviour at L/L_Edd<0.2: the ultraviolet emission properties show much weaker
trends, and no longer agree with QSOSED predictions, hinting at changes in the
structure of the broad line region. Overall the observed emission line trends
are generally consistent with predictions for radiation line driving where
quasar outflows are governed by the SED, which itself results from the
accretion flow and hence depends on both the SMBH mass and accretion rate.
