Using a WiFi extender certainly helps but without the option of recording to an sd card there WILL be some dropped frames recording over wifi. I use the mi WiFi 2 extender and it eliminates most of the dropped frames, it’s a cheap investment and well worth it imo.
Tello2 will hopefully include a $5 card reader.
Put your video bitrate in auto. The Tello software will auto adjust and prevent most of the frames from dropping. Can also switched to aTello app. The programmer, made the software to prevent frames from dropping, but what you get in return is garbage in the frame.