It is all CAT-6. Even the 350' "crimp your own" kit is CAT-6.
And a good thing too. USB 2.0 has a max transfer of 480 MBits/sec. CAT-5 is good for 100 Mbits/sec.
Mouse lag? Let's see - about 4 msec through each adapter and 2 msec through the cable ... no, kidding.
If it works, you will need expensive, lab grade equipment to measure any lag present.