I am seeking for some clarification in using Population in salesforce marketing cloud.The scenario is i have data coming from the salesforce through Marketing cloud connector.And i have Person Accounts and many related objects.My question is should i create a population with person account and then create data relationship with other objects? As only the attributes in the Person Account or the related objects will be used in email journey, my assumption is we need to create population using the Person Account DE.
There are a lot of ambiguity around Populations in SFMC. Populations define contact information for contacts (representing a subscriber).
Populations are essentially used to tell the SFMC system that your basic contact information such as Email Address may be different for certain types of contacts.
A simple way to think about it is if you have multiple sources of data types coming from different source systems. For example if you have different email address sources, you can use the population model to tell the SFMC system to use the correct email address field depending the source system.
If your Person Account is your only type of contact information, you likely do not need to use the Population model.
Here is some more information on Populations from the Trailhead:
Populations are used to categorize distinct subgroups of contacts. Think of a population as the subset of the master list of people who could enter a journey. Let’s say you work for a car transportation company and you have one master table of contacts, which includes both riders and drivers. You can create two different populations: one population for the drivers, and another for the riders, since separate marketing efforts and data structures are required for each group or population.
If you’re using the most up-to-date Journey Builder functionality, you won’t need to use populations most of the time. Instead, it's best to save populations for specific use cases where you need to create complex queries, such as if your account uses field-level encryption or when you’re using API Entry Sources in Journey Builder.
Also see this related question if you need to use populations for Journey Builder.
In terms of performance, Populations are not recommended to be used for more than 3 entities.