Within the Ads tool when creating events it would be helpful to assign these to specific brands/business units. This would ensure that lifecycle stage change events, or form submission events, are sent to the ad networks only for contacts linked to that brand.
The reason for this is that each brand has a different customer base. If a customer lifecycle stage change is synced to Google Ads and used for optimisation it becomes less effective when the data includes customers from every brand in the account rather than just the audience for that brand.