ADC resolution vs Accuracy of signal measurement?
Generate an error budget.

for each voltage divider

for each opamp

for each Switching Regulator that will inject trash into Ground and into Rails

know the PSRR for each opamp, at switch_reg ringing frequencies

injected trash, from line_voltage switch_regs that couple electrostatically (displacement currents) into your high impedance voltage dividers

how to initially set the signal_chains to be &quot;accurate&quot; (that is, calibrated)

how often to reexamine the Calibration.

Must the system remain 0.1% or better for 40 years in orbit?


Your goal of 0.1% (does someone DIE if that is not met? or just get Least Significant Digit flicker on a display?) can be met by 10 bit ADC but requires an error budget that is extreme for all the other error sources.
Thus 12 bits or 14 bits (with Temperature Stability spec'd in the ADC data sheet) is more reasonable.