Observations of quasars at the highest accessible redshifts have revealed supermassive black holes (SMBHs) with masses much too massive to be accounted for by the growth mechanisms observed in the local universe. Masses up to 10 10 M ⊙ up to z~7 seem to suggest some type of secular evolution or external influence to feed the earliest SMBHs at extremely high rates. Observations at such redshifts come at expensive technical cost and require significant dedicated space-telescope observing time. However, in the z~4 regime, SMBHs are still relatively young, exhibit extreme growth rates, and are economically accessible for both frequent shallow snapshots as well as deep observations. In this dissertation, the accretion mechanisms of z~4 quasars and the structure of their host galaxies and nearby companions are investigated to search for evolution over cosmic time as well as outside influence on star formation rates (SFRs) and SMBH growth. Building the longest available X-ray light curves of four representative radio-quiet quasars, X-ray variability is evaluated at timescales from days to years in the rest frame, and robust simulations allow both qualitative and quantitate measurements of variability to compare with samples at lower redshifts. At all timescales, X-ray variability is consistent with or lower than lower-redshift samples and no evolution is observed. To investigate regions outside the central quasar, deep rest-frame UV observations of six similar quasars whose hosts exhibit highly varying SFRs are used to map the structure of star forming regions in the host galaxy and investigate the sky density of nearby sources. Despite the suggested hypothesis that major galactic mergers influence high SFRs, no evidence of merger scenarios is shown in the high-SFR sources, and the lower-SFR, which were thought to reside in sparse environments, also reside in dense environments.