AppDynamics imposes a limit on the number of Service Endpoints that can be registered per node to ensure manageable performance and overhead. The limit per node is set to 100 Service Endpoints, which is a balance between providing detailed monitoring and maintaining application performance.
References:
AppDynamics documentation on Service Endpoints:
https://docs.appdynamics.com/latest/en/application-monitoring/monitor-service-endpoints

Data collectors in AppDynamics supplement business transaction and transaction analytics data with application data by capturing additional information during transaction execution. This can include method arguments, return values, and invocation context, which enriches the transaction data with more detailed application-level insights. This capability is crucial for in-depth performance analysis and troubleshooting, providing a more comprehensive view of application behavior.
References:
AppDynamics documentation on Data Collectors: Explains how to configure data collectors to capture and display detailed application data within business transactions.

In AppDynamics, metrics from different applications can indeed be cross-referenced on a single dashboard.
This allows for a more holistic view of an organization's application ecosystem, facilitating the comparison and correlation of performance metrics across different applications within the same AppDynamics controller.
References:
AppDynamics documentation on Custom Dashboards: Details how to create custom dashboards that can include metrics from multiple applications, enabling cross-referencing and comprehensive performance monitoring.