Cool.I'm fortunate to have not noticed any control lag using Copilot, so I'll pass on 1.4c... the only annoyance I have is having to click OK on the beta disclaimer every time I open 1.4b (full version) on my phone but I can live with that until the production version.
In fact, early yesterday morning I got bored and felt like experimenting for a while. Just for kicks, I dug out and charged up two old tablets, a 2015 Fire 7 running the original Android 5 fork it came with, and, believe it or not, an old (very slow) Nextbook 8" with a very strange version of Android 5.0.
Installed Copilot 1.4b on those, also used my M3 tablet as a copilot, and S5 phone as control device.
With the tablets sitting side-by-side on the bar, I flew a full battery around the kitchen with no problems and no noticeable video or control lag... and was duly impressed.
The crucial point why you don't have issues is that you are not using bluetooth. Add bluetooth and all sorts of troubles appear.
But: 1.4b is already final in the play store. Just leave the beta test program and you will get it, without the beta test message.
Or stay in Beta and try the 1.4c which brings the reduced bitrate :-(