To meet the requirement of granting Read/Write access to child Opportunities for Account Team members with the Executive Sponsor role, an Opportunity sharing rule should be created. Sharing rules in Salesforce allow you to automatically extend access to users based on their roles or other criteria. In this case, the sharing rule would be configured to provide Read/Write access to Opportunities for those in the Executive Sponsor role on the Account Team.
References:
* Sharing Rules Overview
* Create and Edit Sharing Rules

To associate contacts with multiple accounts, using the Contact to Multiple Accounts feature is the ideal solution. Here's why:
Built-In Feature: Salesforce provides the Contact to Multiple Accounts feature as a standard capability, allowing a single contact to be associated with multiple accounts without needing custom fields or objects.
Relationship Management: This feature allows users to specify the role of the contact in relation to each account, which helps Cloud Kicks manage complex relationships across various accounts.
Salesforce Best Practices: Salesforce recommends utilizing standard features like Contact to Multiple Accounts to avoid unnecessary customization and ensure compatibility with Salesforce updates.
Reference:
In summary, using the Contact to Multiple Accounts feature (Option A) is the recommended approach for associating contacts with multiple accounts.

EAC a two-way sync for events and contacts means that EAC can synchronize events and contacts between Salesforce and the connected email and calendar applications, such as Gmail or Outlook. This minimizes the need for sales reps to manually create meetings and events that are stored on their calendars, as they will be automatically captured and displayed in Salesforce.
EAC supports emails, events, and contacts means that EAC can capture these types of activities from the connected email and calendar applications and display them in Salesforce. This allows sales reps to view and track their interactions with customers without having to manually log them in Salesforce.