If I understand your question, you want to restrict the standard Account (1) to Contact (Many) relationship to 1:1, using declarative tools.
Assuming that to be the case, you can do so. If not completely declarative, you can still achieve it with minimal customization. You can achieve it using one of the approaches as below:
- Create a field on Account, which keeps count of Contacts associated to that Account
- Create a Validation Rule on Contact which will be invoked whenever a new Contact is getting created. The Validation rule just verifies as
if Contact count on associated Account > 1, restrict the creation
Person Accounts are just another type of Accounts and you use that specifically in scenarios where your Business model is B2C. It can co-exist with Business Accounts when enabled.