"You can only add Project Online to a site collection that uses the Classic Team Site or Project Site template."
I am new to Project Online and SharePoint. What are the implications of using one template or the other? Or will both behave exactly the same so far is Project Online is concerned? I understand that you can't change templates after a site collection is created, so I want to make sure I don't paint myself into a corner.
Both will provided the same capabilities for PWA. I would provision a new Project Web App site collection from the SharePoint Admin Center, Create > Other Options > Choose a Template - select Project Web App site: