How simple can a bar band get away with, rehearsed and prepare for it. Assume all decent/good-quality equipment.
Mixing from stage,
Passive mixer with on-board FX (no outboard processing),
All powered speakers-- subs, with fronts and monitors being the same cabs,
one monitor mix, full mix, same as the fronts,
disciplined musicians balancing their own vocals/instruments individually from what they hear in the monitors.
all instruments direct (