We have service providers as a contact record who should be accessing D365 records (Custom entities, Quotes, Service modules) using a mobile app and update information on their end. 

For this a native app (react js) was built. So the idea is if the service providers log on to the mobile app, they should be able to see the quotes and jobs assigned to them against their contact record. 

The question is how can we achieve this.

1. What should be the integration tool used to connect react.js app and D365 (online)?

2. Can we use just one service account to retrieve the information from D365? As the service providers will see only the associated entities information related to their contact record.

Thanks in advance.