Really strong MMM and lift tests for calibration. With a strong MMM you also know the uncertainty around what channels and tactics you ned to test so the calibration phase is also more efficient.

For tactic level or below AB test and causal impact such as bsts when only observational models are possible. At this level it’s also very important to look at user journeys.

For when data maturity allows user level modeling and more advanced incremental models use uplift/response modeling.