GCP FireStore: 'Map of Maps' VS 'Array of maps' datatype

Question

Scenario: Entity A is parent, B is child of A with 1 to many, C is child of B with 1 to many. Lets say: A is account, B in Contact & C is Address

We need to have entire structure in 1 document, so no sub collections & sub documents. For child entities we have 2 options: Map of Maps or Array of Maps. We are inclined towards 'Map of Maps' as we can't set a unique Id at array on top level. It has to be a field inside the array and then its difficult in script to search with it as we need to loop through all records.

So configuration will look something like this: - Define a field of type Map inside Account with name Contact - Contact will only have fields of type Map inside it. Each map field name is unique id of contact. So lets say 2 maps: ContactId1, ContactId2 - Inside ContactId1 map we will have some Contact field like names and then we will have another field 'Address' of type Map. - 'Address' will only have fields of type map inside it. Each map field name is unique id of an Address : AddressId1, AddressId2 - Map AddressId1 will have fields inside it for address i.e. StreetName, No, City, Zipcode, etc

Questions:

• Is 'Map of Maps' datatype better approach then 'Array of maps' datatype for our scenario
• What are the pros and cons of both approach

Account{
    Name: "My Account Name"
    Contact:
        Contact123:
          FirstName: "F1"
          LastName: "L1"
          Address:
              Address1231:
                   Street: "Street1"
                   City: "City1"
              Address1232:
                   Street: "Street2"
                   City: "City2"
        Contact234:
          FirstName: "F2"
          LastName: "L2"
          Address:
              Address2341:
                   Street: "Street3"
                   City: "City3"
              Address2342:
                   Street: "Street4"
                   City: "City4"
}