1. I have ethernet plugged into both airport express devices, neither show an option to extend by ethernet
"extend by Ethernet" will only appear if you are using the AirPort Utility setup "wizard" to configure the AirPort Express from scratch. In other words, the wizard assumes that you have reset the AirPort Express back to factory default settings and you are setting it up again from scratch. Post back if you want to go through the setup using the AirPort Utility setup "wizard".
If you don't want to start all over again and set up the AirPort Express from scratch, the correct setting for the AirPort Express is "create a wireless network", since "extend a wireless network" and "join a wireless network" are settings that are used only when the AirPort Express connects using wireless. But.....you indicate that you are using Ethernet.
5ghz, under the wireless tab when you click the wireless options, it gives an option to create a 5ghz network name. I was under the impression the airports (both extreme and express) bounced back and fourth from 2.4 to 5ghz depending on whatever network was performing better.
The Extreme and Express do not "bounce back and forth". By default, both AirPorts are always providing both a 2.4 Gz and a 5 GHz signal that use the same wireless network name. It is up to wireless devices to choose the best signal to which to connect. This is Apple's default or recommended setting for the AirPorts.
If you place a check mark in the box next to 5 GHz Name, that will assign a different name to the 5 GHz network, so the 2.4 GHz signal will have one network name and the 5 GHz signal another. Users who feel that it is important for devices to connect to the 5 GHz network use this type of setup, so they can "aim" a wireless device at the 5 GHz network, rather than letting a wireless device choose between the available 2.4 GHz and 5 GHz signals in the default type of setup.
Good arguments can be made for either type of setup, and as you might imagine there are upsides and downsides to each approach. If you decide that you want to assign a separate name to the 5 GHz network, you would want to do this on all of your AirPort devices....the AirPort Extreme and both Express devices.