I also have both AZ80 and AZ100. AZ100 also has an internal acoustic control chamber that is possibly smaller than the one in AZ80, due to overall reduction in earbud size for the former.
Agree that AZ80 has a more holographic soundstage, though the AZ100's soundstage is still relatively wide for a TWS with overall greater clarity and less distortion than the AZ80.
As mentioned by
@DigDub, the AZ80's tuning is more V-shaped with perhaps a slightly recessed mid-range. AZ100's tuning comes across as more balanced with a flatter-tuned midrange, resulting in vocals shining more via a slightly more forward vocal presentation.
Overall, I would say the AZ100's soundstage is balanced somewhere in-between the AZ80 (very wide) and Pi8 (intimate).
If you prefer sense of a wider soundstage, you may also use the Technics app EQ to cut the midrange frequencies by 2-3 notches, resulting in vocals being slightly recessed but also a wider stage presentation.