I stay with factory, to me it's easier to get used to that once than to try and change things and constantly having to try to relearn how it behaves after each change.
Seems I didn't remember right since I don't really use that workflow, LosslessCut doesn't maintain it, but you can do it directly in GyroFlow. When you go Open File you can select multiple, it then provides you with an option to join.
How does it behave if you try to take off directly in manual mode?
Likely the hardcoded gains are simply mismatched to the new powertrain. Seen many people having problems with this mod, would just not recommend it.
The Goggles 2 and 3 have built-in diopter adjustments, plus come with additional lenses for more. The V2 don't have any adjustment.
So you're less likely to need a 3rd party solution with the 2 and 3, but some are available if you do.
Like older models it doesn't and it's up to you to choose the RTH height wisely for the environment you're in. You should always be doing that anyway, OA is just there to give you a 2nd chance in case you made a mistake.
The Goggles 3 adjust well to me, picture's clearer than the 2 although smaller.
The FPV controller 3 is basically the same as the 2 I was using with both the DJI FPV and Avata, the removal of the flip-out antenna is welcome though.
Size. Every step they've been sized down because people...
What exactly are you after? If the goal is "analysis of how a drone that'd be used for work purposes can get hijacked by jamming / overpowering the protocols you mentioned" you're about 5-7 years too late for that, it's been done already and none of the serious models you'd use for work will be...
Yeah, just long press the button on both the Avata and the RC. If that doesn't work then download DJI Assistant for FPV series and upgrade the controller.