RHEL AMI questions

From what I can tell, the ec2-net-utils package doesn't contain drivers, rather it's scripts and udev rules to support the adding of additional ENIs. You can look at them in detail on an Amazon Linux instance:

ec2-user@ip-172-31-0-39 ~]$ rpm -ql ec2-net-utils
/etc/dhcp/dhclient.d/ec2dhcp.sh
/etc/init/elastic-network-interfaces.conf
/etc/modprobe.d/ixgbevf.conf
/etc/sysconfig/modules/acpiphp.modules
/etc/sysconfig/network-scripts/ec2net-functions
/etc/sysconfig/network-scripts/ec2net.hotplug
/etc/udev/rules.d/53-ec2-network-interfaces.rules
/etc/udev/rules.d/75-persistent-net-generator.rules
/sbin/ec2ifdown
/sbin/ec2ifscan
/sbin/ec2ifup
/usr/share/man/man8/ec2ifdown.8.gz
/usr/share/man/man8/ec2ifscan.8.gz
/usr/share/man/man8/ec2ifup.8.gz

You can still at multiple ENIs in RHEL, you just don't have those scripts to help with it.

On the support question there's good info on this in the RHEL Partner FAQ:

"Q: How does support work for Red Hat Enterprise Linux on Amazon EC2?

All instances of Red Hat Enterprise Linux on Amazon EC2 will receive updates at the same time that updates are made available from Red Hat. To be notified when updates are available, subscribe to Red Hat Security Announcements. Updates can be installed using standard Red Hat systems management tools. Additionally, Red Hat Enterprise Linux on Amazon EC2 is covered under AWS Premium Support. AWS Premium Support customers can contact AWS for help to resolve issues that are related to Red Hat Enterprise Linux on Amazon EC2. AWS Premium support will facilitate resolution with Red Hat support for any issues that require escalation. AWS customers using RHEL will not contact Red Hat directly unless they have purchased EC2 through Red Hat Cloud Access and have a direct support agreement with Red Hat."