If I was shopping for a 4k cable, I'm not sure why I would bother with an 18 Gbps cable these days instead of the modern spec 48 Gbps ones. Granted, the faster ones are more finicky at distances over 10 feet, so you may want an active or an fibre-optic cable instead and that does tend to be more expensive.
18 Gbps will do 4k 60Hz 10bit 4:2:0, but your LS12000 is already rated to support 4k 120Hz so I would just go full speed now and buy once instead the half measure.