  PIP-II is an essential upgrade of the Fermilab complex that will enable the
worlds most intense high-energy beam of neutrinos for the international Deep
Underground Neutrino Experiment at LBNF and support a broad physics program at
Fermilab. Ultimately, the PIP-II superconducting linac will be capable of
accelerating the $H-$ CW beam to 800 MeV with an average power of 1.6 MW. To
operate the linac with such high power, beam losses and beam emittance growth
must be tightly controlled. In this paper, we present the results of global
optimization of the Linac options towards a robust and efficient physics design
for the superconducting section of the PIP-II linac. We also investigate the
impact of the nonlinear field of the dipole correctors on the beam quality and
derive the requirement on the field quality using statistical analysis.
Finally, we assess the need to correct the quadrupole focusing produced by Half
Wave, and Single Spoke accelerating cavities. We assess the feasibility of
controlling the beam coupling in the machine by changing the polarity of the
field of linac focusing solenoids
