The front ones often get a warning that I could be getting better data rate.
There's your check...
It's easiest to read the manual for the motherboard. It will tell you which ports integrated into the rear panel are USB 2 / 3. It will also tell you which headers on the motherboard are USB 2 / 3. You can't connect a front panel USB I/O cable to a USB 3 mobo header and vice-versa. Simple.
Bear in mind that USB includes the device, the socket and cabling and the motherboard header - you can't have any USB 2 components (e.g. cable extender) between a USB 3 device and a USB 3 port or header, otherwise you will drop to the lower speed.
You can also have USB ports on a PCI / PCIx / PCIe expansion card - in this case the speed from the device to the system will be dictated by the lowest speed of either the PCI bus or the USB version.
For example, I've put a USB 3 PCIe V2 card into an older PC that only supports PCIe V1, so the limiting factor is the PCIe throughput, giving me USB 2.5, in effect!
SD