Azure App Service Plan and Resource Group Planning

Question

We are migrating all our 25 portals to Azure. All these portals point to a single database. These websites are associated with 25 different companies who are customers of our client.

We have planning to have the structure something like this. (1) Create 25 Resource Groups (2) Create 25 App Service Plans (3) Create 25 App service - Web apps

My Questions:

1. Is it suggested to have both the web apps and the database (SQL Database) in the Same Resource Group?
2. We would like to leverage the auto-Scale-Out feature separately for each of our portals and so we planned to have a separate App Service Plan. Is that good?

Thanks,

Prawin