Nice guide and I do not dispute any of it as it all makes logical sense. I do wonder how much of it is really necessary.
I fly with an iPad Air (1st version)
I regularly leave 4-5 apps on
I never turn on airplane mode
I never restart before flying
I leave background refresh on
I've never turned in hardware decode (not saying this is better but my lag is negligible so my logic is, if it ain't broke don't fix it)
It's the cellular model and I have flown both when the map is downloaded from GPS and near my house where it's downloaded via wifi.
I've never had the app crash (I did have it loose video signal when it claimed full bars a couple of times but both were with a perticular app version and it's not happened since updating which makes me think that was a software bug). I've never had a "fly-away" or lost control, I've not experienced shortened range (though I'm not regularly pushing it to the limit)
Now this MAY be luck, and I MAY come crawling back with my tail between my legs later but what I'm trying to say is your P3 is not going to decide to hurtle towards a bunch of nuns while spontaneously bursting into flames and opening a worm-hole to hell if you do not follow all this every flight. At the end of the day none of this is mentioned in the manual and (you would like to assume) safety is DJI's top priority (even if it's because it affects their profit rather than for moral reasons)
Stop stressing, use comon sense, JUST FLY