I try and track people based on footsteps - above and below too. Im not using wall hack but listening for footsteps and aiming at the steps.
Yes, obvious wallhack if its out of footstep sound distance but there are some headphones/soundcards/headphone amps where you can enable 'scout mode' which boosts high frequencies of footsteps. Dolby Atoms also makes it a bit easier
Personally I use Atmos but not any of the scout modes. I do boost some higher frequencies on an EQ because the headphones I have (Beyerdynamic DT1770) are bass heavy compared to the AKG 702s I had before them
Granted there are some cheaters but my guess is wallhack will be on the lower end of the cheating scale. Those hardware devices that plug in to give recoil control and aimbot cheats will be much higher.
I can still take whole teams out my myself in Plunder trios so the cheats are not that rife, or they're just rubbish at cheating too

I'm really enjoying getting up and taking control of what I call 'Hamburger Hill' on Plunder. Make your way up to the peak of B4 from B5 / B6 on the out of bounds border line. It's hard work but great fun with a sniper and mid-long range AR - by yourself it usually is anyway. Once there you have your pick at people flying ovrehead into storage town