The iPhone 7/7 Plus (seem to) natively utilise the ear speaker for stereo sound, making Handsfree Mode redundant.

The microphone in Handsfree Mode is right next to the ear speaker, making other users voices feed back to them, making me turn the Voice Activation Level up to avoid that feedback, which then requires me to speak very loudly to even register my voice.

The solution to this is disabling stereo sound only within the Teamspeak app. I'm not sure that's at all possible as it seems to be native within iOS. Hopefully there can be a workaround as this is quite frustrating.