All batteries heat up with use to some degree. I checked my Mav 3 battery temps after flying ... probably at -10F but I don't recall. Their temp did not appreciably change. I see little loss (some) of flight time at those temps but with smaller...
H265 is more efficient allowing lower bit rates and therefore smaller file sizes. It requires more work from the computer so older machines have a hard time with it and can require longer rendering and choppy playback (dropped frames) for older...