How to vocal syncing in ableton (when the music is played live)
1.) Acquire Acapella and the full mix

2.) Disable any warp markers made before, by selecting both tracks (shift+click) and double clicking the "warp" button, or clicking on separate tracks and selecting "warp 120 BPM from here" from the warp marker right click menu.

3.) synchronize both tracks as good as possible (If you hear comb filtering on the vocal track, you're good)

4.) If the full mix is brickwalled so you can't see the drum hits, you may want to use a lowpass fliter on the full mix and freeze it so the waveform changes and probably you can now see kick hits. Select both tracks and Consolidate so both tracks are the same length.

5.) Select both tracks. Click "Reset warp markers"

6.) Click on the vocal track, press Shift, Click on the drum track, and you should see the Clip View of the drum track/full mix.
If you've done everything properly, when you add and drag warp markers of the drum track in the clip view, the other track should also bend accordingly. Use this to warp the tracks to the master tempo (you can enable the metronome for help

When you're done, check if the vocal track is warped correctly, export the vocal track and delete temporary files made when consolidating. Enjoy your perfectly-synced acapella