This is a copy of the settings you need to add to steamvr.vrsettings while using the OpenVR Leap Motion drivers https://github.com/cbuchner1/driver_leap

LeapVRSettings.vrsettings

{
   "driver_null" : {
      "displayFrequency" : 90,
      // drivers are searched in alphabetical order, so you may need steamvr.forcedDriver="null" as well
      "enable" : true,
      "id" : "Null Driver",
      "modelNumber" : "Null Model Number",
      "renderHeight" : 1512,
      "renderWidth" : 1344,
      "secondsFromVsyncToPhotons" : 0.10000000000000001,
      "serialNumber" : "Null 4711",
      "windowHeight" : 1080,
      "windowWidth" : 1920,
      "windowX" : 100,
      "windowY" : 100
   },
   "leap" : {
      "gripAngleOffset_lefthand" : 0,
      "gripAngleOffset_righthand" : 0,
      "renderModel_lefthand" : "vr_controller_vive_1_5",
      "renderModel_righthand" : "vr_controller_vive_1_5"
   },
   "leap_gestures" : {
      "GrabPressed" : "GestureWithin:LowerFist[0.5,1.0]",
      "MenuPressed" : "GestureWithin:FlatHandPalmTowards[0.5,1.0]",
      "SystemPressed" : "GestureWithin:FlatHandPalmAway[0.5,1.0]",
      "TouchpadAxis[0]" : "GestureAxis:ThumbPositionX[-1.0,-1.0]",
      "TouchpadAxis[1]" : "GestureAxis:ThumbPositionY[-1.0,-1.0]",
      "TouchpadPressed" : "GestureWithin:Thumbpress[0.5,1.0]",
      "TouchpadTouched" : "GestureWithin:Thumbpress[0.0,0.5]",
      "TriggerAxis[0]" : "GestureAxis:TriggerFinger[0.0,1.0]",
      "TriggerAxis[1]" : 0,
      "TriggerPressed" : "GestureWithin:TriggerFinger[0.5,1.0]"
   },
   "steamvr" : {
      "activateMultipleDrivers" : true,
   }
}

Copy your steamvr.vrsettings and rename them to LeapVRSettings.vrsettings and add the lines from this gist where they go in it to enable the OpenVR Leap Motion drivers. It's required that you install them so check the GitHub here and get the latest release.

This goes with my batch file that swaps between LeapVR mode and Vive mode with a single click.