The trail options (aka the length and width) only works on Surf easy, on any other server it's the default trail width and length no matter what you set it as.
Probably goes back to when it was 30+ players on a regular basis, having a bunch of long trails could have caused some crowding/view issues. The trail atm on Easy is longer than intended when at max length, not sure what caused it but it's just not been fixed, kind of become norm now though. It should last 1-2.5 seconds before fading, not 5 or whatever it is now. You should still be able to alter the length and width on any server though.