The following limitations should be considered before enabling Person Accounts in Financial Services Cloud:
Person Accounts cannot be disabled once they were enabled. Enabling Person Accounts is an irreversible action that affects your data model and user interface. You should carefully evaluate your business needs and test the functionality in a sandbox or developer org before enabling it in production.
Creating a client record via Salesforce Inbox is not supported. Salesforce Inbox is a feature that allows you to access Salesforce data and actions from your email application. However, you cannot use Salesforce Inbox to create a client record as a Person Account. You can only create a client record as an Individual Model record using Salesforce Inbox. Verified Reference: : Salesforce Help Article 4 : Salesforce Help Article 5

To configure Financial Services Cloud to allow users to relate two business accounts, the administrator should update the Role picklist on the Account-Account Relationship object with new value. The Role picklist is a field onthe Account-Account Relationship object that defines the type of relationship between two accounts, such as Household Member, Business Owner, Trustee, or Friend. The Role picklist is used to filter and display the account-account relationships in the Actionable Relationship Center (ARC). To update the Role picklist, you need to go to Setup > Object Manager > Account-Account Relationship > Fields & Relationships
> Role and add or remove values according to your business needs. Verified References: : Salesforce Help Article [10] : Salesforce Help Article [11]

The following records support Document Checklist Items out of the box in Financial Services Cloud:
Account: An Account is a record that represents a person or an organization that has a business relationship with your company. You can use Document Checklist Items to request and track documents from your account holders, such as identity proofs, tax forms, or contracts.
Residential Loan Application: A Residential Loan Application is a record that represents a request for a loan to purchase or refinance a residential property. You can use Document Checklist Items to request and track documents from your loan applicants, such as income statements, credit reports, or property appraisals.
Opportunity: An Opportunity is a record that represents a potential sale or deal for your products or services. You can use Document Checklist Items to request and track documents from your opportunity owners, such as proposals, quotes, or agreements. Verified Reference: : Salesforce Help Article 2 : Salesforce Help Article 3 : Salesforce Help Article 4