One of the things missing from vanilla AE2 is a way to find out how many channels are free on a cable.
With that I mean how many devices can you hook up before you steal a channel from somewhere else/run out of channels.
Once you have a decently sprawling organically built base you are not going to keep track of how many channels you have free on the yellow line next tot he smelting area
That is what the smart cables are for. The white/blue lines indicate how many channels are in use. Also, the network tool may show this information as well. Been a while since I used it so I'm not sure.