Speed of 1000 Base KR
1000Base-KX in full-duplex mode is made of two differential pairs : one differential pair for TX @ ~1GHz and another differential pair for RX @ ~1GHz.

10G Base-KR in full-duplex is made of two differential pairs : one differential pari for TX @ 10.325 GHz and another differential pair for RX @ 10.325 GHz.

These two specifications are backplane-oriented, thus are made for copper on PCB transmission (beware of signal attenuation @ 10GHz and also @ 1GHz).

1000Base-KX is derived form 10G Base-KR and if you can find quite a few tutorial/articles on the internet about 10G Base-KR, 1000Base-KX is almost unknown : I had to make an eye diagram and check if the 1000Base-KX signal was compliant with the IEEE standard, I contacted the Tektronix support to retrieve the mask, the support engineer never heard about 1000Base-KX before me...

Also as 1000Base-KX was defined at the same time as 10G Base-KR, the last one was widely used (Datacenter/server oriented), thus the more documentation about it.