The below videos provide an insight to how you could gain valuable performance information for your applications estate using Azure Application Insights.
Azure Application Insights is not restricted to Azure applications only, this link shows you how to use the solution for your on-premise applications also.
Azure Monitor and Application insights can combine to provide you with true end to end monitoring and alerting capabilities, this is essential especially as you're migration your applications in Azure and need to understand their usage and also understand if you have over or under specced your plans.
A4S has deployed this solution into its clients with great success often allowing the consolidation of many monitoring platforms into one, we have also overlaid the solution with Grafana for highly detailed visualisations.
If you need help in this area or would like more information then please get in contact.
Thanks for reading, Jason