Bluetooth. Haven't tried otg. The app lets you set the stick sensitivity also. That's the bad thing about the Gamesir with the Tello app, its really touchy. I use a cheap ps3 controller via otg with aTello..
I use the different apps for different reasons, but prefer the aTelloPilot with the Flypad as I have used it for so long with my Bebops. I use the Ryze app for close in fpv though its a bit laggy. ATello is good also but only works with the ps3/otg. Its less laggy that way.
So just updated the aTelloPilot app. It now supports the T1d. I also got it to work with the ps3/otg once. This app has a stick tuning mode. Allows you to see the stick movments. The Flypad and the ps3 have nice slow linear movements. The T1d moves much too fast. Thats why its so jumpy. I have flown with it a good bit but much prefer the smother movements of the Flypad/ps3. If one is going to use this app the best controller by far is the Flypad! I'm retiring the T1d.