1. Haven't tried. I do have lots of lag on youtube on Android 10.
2. Still testing on my recently acquired pair. At 20% XM3 volume, 100% phone to the 20% battery warning I get about:
3:40 on AAC or SBC with EQ and NC on (about 4:40 they turn themselves off).
4:30 AAC and EQ, no NC.
7:30 AAC only, no EQ or NC. (9:20 turns off).
Edit, update:
5:20 AAC & NC, no EQ (6:40 turns off).
5:15 SBC & NC, no EQ.
Still have to try AAC & NC only (and maybe the last few combinations). The EQ's digital processing appears to use the same amount of battery as the DSEE HX.
3. Never heard them and can't compare them.
4. Comfort for me is ok but they aren't super stable. I am able to wear them for that 9+ hours straight. The trick is getting comfortable tips that still seal and rotating so they also rest against the anti-tragus. This keeps the weight away from the ear canal.
5. Plenty loud unless your stuck with the EU version, which has a reduced output. I play volume at 20-40% and it's plenty. 50% and it's not something I'd want to listen to for extended periods.