Market Place for AMI: https://aws.amazon.com/marketplace/
paravirtual (PV) or hardware virtual machine (HVM).
The main differences between PV and HVM AMIs are the way in which they boot and whether they can take advantage of special hardware extensions (CPU, network, and storage) for better performance.
For the best performance: current generation instance types and HVM AMIs
Amazon EC2 Instance Types
https://aws.amazon.com/ec2/instance-types/
Ubuntu Locator of AMI
https://cloud-images.ubuntu.com/locator/ec2/