1. Driver support for Enhanced networking
Enhanced networking uses single root I/O virtualization (SR-IOV) to provide high-performance networking capabilities on supported instance types. SR-IOV is a method of device virtualization that provides higher I/O performance and lower CPU utilization when compared to traditional virtualized network interfaces. Enhanced networking provides higher bandwidth, higher packet per second (PPS) performance, and consistently lower inter-instance latencies.
Earlier versions of ixgbevf driver, including the minimum recommended version, 2.14.2, do not build properly on some versions of Ubuntu. The 2.16.4 version of ixgbevf should be used for Ubuntu instances. You will be able to find more details regarding the same by following link.
2. EBS–optimized instance
An Amazon EBS–optimized instance uses an optimized configuration stack and provides additional, dedicated capacity for Amazon EBS I/O. This optimization provides the best performance for your EBS volumes by minimizing contention between Amazon EBS I/O and other traffic from your instance.
However, it is not enabled by default on some instance type and you would need to enable the same. You will be able to find more details regarding the same by following link.