The SUW from Innerleithen taking in bits of the Selkirk Marathon route has a good combination of fast and tech terrain although some of the bits in between may be a bit dull eg short road/fireroad sections etc.
As above the Enduro trails at Inners and GT will also give you a good mix.
Gypsey Glen is fast when dry and can be done in conjuction with some fo the GT Enduro/off piste stuff.
TweedLove do local rideouts where they show folk around may not be one on the dates you are up but worth keeping an eye on the site for updates
http://tweedlove.com/events/2014-events/local-ride-outs-2014
I am not in the Strava family so don’t have anything i can send unfortunately but would be happy to show you around if i am about on 18/19th
Cheers