Unified CloudWatch Agent allows collection of system level metrics and logs from EC2 and on-prem servers. (Unified Agent must be installed and its metric data is in addition to the default EC2 metrics - like CPUUtilization, DiskReads and StatusChecks).

If you need in System Level Metrics ( like memory and disk-usage) you have to use Unified CloudWatch Agent.

Unified CloudWatch Agent is also very useful to collect logs from terminated instances (ie, in autoscaling groups)

LogInsights can analyse our logs with interactive queries (and display them with different visualisations)

Container Insights capture additional diagnostic data (at cluster, node, pod and task level) from your containers (EKS - ECS)

Similarly Lambda Insights provide additional information about Lambda functions.

Logs can be sent to S3, Kinesis Data Streams and DataFirehose, and can be exported to Amazon ElasticSearch for real-time log processing with subscription filters.