It's possible that using the same name on each radio would would as long as the device your trying to connect to would pick the higest supported band. I think people get in the frame of mind, at least for me, to name each band differently for ease of use and identification. I would recommend if you have deviced that support both 2.4 and 5Ghz, I would name them differently.
To tell the speed of the devices that are connected to the router, look on the Status Page/Wireless. Will show you whats connected and at what speeds.