Well, clients like nodus and the iridium client are hard to block. The plugin NoCHeatPlus can block most of their features on vanilla but for ftb it will just kick everyone that even uses jetpacks. What I use is world guard and set the flag for regions at all warps to survival only and then only ops/owners of the region can have creative, and I have regions like this around a large distance from spawn and other areas making the people with these clients think it doesn't work and 99% of the time they just leave.
