  Moir\'e superlattice-induced sub-bands in twisted van der Waals homo- and
hetero-structures govern their optical and electrical properties, rendering
additional degrees of freedom such as twist angle. Here, we demonstrate the
moir\'e superlattice effects on the intralayer excitons and trions in a twisted
bilayer of MoS$_2$ of H-type stacking at marginal twist angles. We identify the
emission from localized and multiple delocalized sub-bands of intralayer
moir\'e excitons and show their electrical modulation by the corresponding
trion formation. The electrical control of the oscillator strength of the
moir\'e excitons also results in a strong tunability of resonant Raman
scattering. We find that the gate-induced doping significantly modulates the
electronic moir\'e potential, however leaves the excitonic moir\'e confinement
unaltered. This effect, coupled with variable moir\'e trap filling by tuning
the optical excitation density, allows us to delineate the different phases of
localized and delocalized moir\'e trions. We demonstrate that the moir\'e
excitons exhibit strong valley coherence that changes in a striking
non-monotonic W-shape with gating due to motional narrowing. These observations
from the simultaneous electrostatic control of quasiparticle-dependent moir\'e
potential will lead to exciting effects of tunable many-body phenomena in
moir\'e superlattices.
