RMII and diferential pairs
Those signals are for a MII port (Media independent Interface), not RMII (reduced MII). None of those signals are differential pairs.

On the other side of the PHY you will find the interface to the Ethernet magnetics (the transformers). These signals are usually labelled TXN/TXP and RXN/RXP. These are differential pairs.

For PCB layout guidelines you should follow the datasheet for the PHY that you're using.