Another update for anybody that cares.
The new .0900 and GO4 4.1.20 on iPad Pro 10.5 (iOS 11.2.1) and using OTG is truly ROCK SOLID!
I just flew a good bit further than I was ever able to previously with my Spark, with rock solid video feed and hardly any RC signal loss the whole flight. Zero feed stutters and no strange events.
The Spark finally performed flawlessly as did the app and RC. Everything was shown on the flight screen including all telemetry and
battery info. There is literally nothing missing/not working using OTG with this setup. I’m only seeing the video feed warning on the top-left of the screen, but that doesn’t bother me as I can see what flight mode I’m in from the top-middle of the screen, next to the GPS icon.
Next I will try without OTG and see if I get the same results on this setup.