It depends what you mean when you say it buffers. If it’s transcoding then one issue is that the LG TV client doesn’t support the video and it’s trying to convert on the fly. If it is, then it isn’t a bandwidth issue.

It’s debatable whether the WiFi on the Apple TV is faster than the LG TV. But it should direct play nearly all videos, and moreso if you use Infuse player (paid app/subdcription).

Rather than running a cable if there’s a free power socket near each end you could buy a couple of units to route Ethernet over power. Not as fast as true Ethernet but much smoother than Wi-Fi for my setup.

LG OLEDS lan is capped at 100mg (that’s why you’re getting the buffering) so unless you get a usb 3.0 to Ethernet adapter the ATV will be much faster (using 1gig lan)