Is Strapi or Notion good products to use to create a full stack application with Users

I am looking to create an investment application for a client which would have Offerings (a deal that you can invest in), Investments (payments that the investor makes to buy into the investment), and Investors (users)

The Investor would be able to see all of the Offerings and all of the Investments that they have made.

I was looking into Strapi and Notion.

Strapi, I found useful because there is a relational db and it has a way to authenticate a user and fetch and update all individual user data.

Notion also has a great way to set up a relational db but I have not been able to figure out how a user would be able to authenticate and fetch and modify only the signed in users information.

Can anyone offer some sort of solution for Notion? I am also open to other products if there are better solutions out there.