Short answer
HubSpot's KB: use the custom report builder to compare engagements, impressions, reactions and clicks across accounts. Social reports show new data within the date range; for example, impressions this week counts new impressions this week.
1. In HubSpot
The relevant screen in my demo portal.

2. Worth knowing
The KB includes sample configurations, such as engagement rate by network.
3. Related
Social reports and the custom report builder.