This blog post explains the difference between these different apps.
Different Types of Apps
Canvas App is a low-code platform for building rich business applications.
Model-driven app design is an approach that focuses on adding components such as forms, views, charts, and dashboards to tables using an app designer tool.
Power Pages is low code / Pro Code software as a service (SaaS) platform for creating, hosting, and administering modern external-facing business websites. We can say an advanced version of Power Portal (Previous Version)