Both HP and Line Out jack are using same Audio Node 0x10 ( share Front Playback Volume)  

if you want Headphone Playback Volume Control, you need to give up grey jack to force driver to use node 0x25


Node 0x10 [Audio Output] wcaps 0x41d: Stereo Amp-Out
  Control: name="Front Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=Out, idx=0, ofs=0
  Device: name="VT1708S Analog", type="Audio", device=0
  Amp-Out caps: ofs=0x2a, nsteps=0x2a, stepsize=0x05, mute=0
  Amp-Out vals:  [0x1d 0x1d]
  Converter: stream=5, channel=0
  PCM:
    rates [0x5e0]: 44100 48000 88200 96000 192000
    bits [0xe]: 16 20 24
    formats [0x1]: PCM
  Power states:  D0 D1 D2 D3
  Power: setting=D0, actual=D0

Node 0x16 [Audio Mixer] wcaps 0x20050b: Stereo Amp-In
  Control: name="Rear Mic Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=2, ofs=0
  Control: name="Rear Mic Playback Switch", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=2, ofs=0
  Control: name="Front Mic Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=4, ofs=0
  Control: name="Front Mic Playback Switch", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=4, ofs=0
  Control: name="Line Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=3, ofs=0
  Control: name="Line Playback Switch", index=0, device=0
    ControlAmp: chs=3, dir=In, idx=3, ofs=0
  Amp-In caps: ofs=0x17, nsteps=0x1f, stepsize=0x05, mute=1
  Amp-In vals:  [0x17 0x17] [0x80 0x80] [0x80 0x80] [0x00 0x00] [0x00 0x00] [0x80 0x80] [0x80 0x80]
  Power states:  D0 D1 D2 D3
  Power: setting=D0, actual=D0
  Connection: 7
     0x10 0x1f 0x1a 0x1b 0x1e 0x1d 0x25


Node 0x1c [Pin Complex] wcaps 0x40058d: Stereo Amp-Out
  Control: name="Front Playback Switch", index=0, device=0
    ControlAmp: chs=3, dir=Out, idx=0, ofs=0
  Amp-Out caps: ofs=0x00, nsteps=0x00, stepsize=0x00, mute=1
  Amp-Out vals:  [0x00 0x00]
  Pincap 0x0001001c: OUT HP EAPD Detect
  EAPD 0x2: EAPD
  Pin Default 0x01014010: [Jack] Line Out at Ext Rear
    Conn = 1/8, Color = Green
    DefAssociation = 0x1, Sequence = 0x0
  Pin-ctls: 0x00:
  Unsolicited: tag=01, enabled=1
  Power states:  D0 D1 D2 D3
  Power: setting=D0, actual=D0
  Connection: 1
     0x16
Node 0x1d [Pin Complex] wcaps 0x40058d: Stereo Amp-Out
  Control: name="Headphone Playback Switch", index=0, device=0
    ControlAmp: chs=3, dir=Out, idx=0, ofs=0
  Amp-Out caps: ofs=0x00, nsteps=0x00, stepsize=0x00, mute=1
  Amp-Out vals:  [0x00 0x00]
  Pincap 0x0000233c: IN OUT HP Detect
    Vref caps: HIZ 50 100
  Pin Default 0x0221401f: [Jack] HP Out at Ext Front
    Conn = 1/8, Color = Green
    DefAssociation = 0x1, Sequence = 0xf
  Pin-ctls: 0xc0: OUT HP VREF_HIZ
  Unsolicited: tag=05, enabled=1
  Power states:  D0 D1 D2 D3
  Power: setting=D0, actual=D0
  Connection: 2
     0x16* 0x25

Node 0x25 [Audio Output] wcaps 0x41d: Stereo Amp-Out
  Control: name="Side Playback Volume", index=0, device=0
    ControlAmp: chs=3, dir=Out, idx=0, ofs=0
  Amp-Out caps: ofs=0x2a, nsteps=0x2a, stepsize=0x05, mute=0
  Amp-Out vals:  [0x00 0x00]
  Converter: stream=5, channel=0
  PCM:
    rates [0x5e0]: 44100 48000 88200 96000 192000
    bits [0xe]: 16 20 24
    formats [0x1]: PCM
  Power states:  D0 D1 D2 D3
  Power: setting=D0, actual=D0