Malfurion, Tyrande, and Illidan kind of go… back and forth in terms of how old they were at the start of the War, the original lore had them as at least full blown adults by the end of the War, so a handful of decades old at least, while the Knaak books turned them into young adult Mary Sue types in their early 20s or late teens. We know this because Tyrande had just recently returned from… priestess school and both of them were agog at how hot she’d become once puberty had hit her (another Knaakism).
Maiev is likely the oldest of current living night elves, but even she is implied to have not been alive during the apex of the empire pre-War, as she speaks of the Night Warrior ritual as if she’d only heard about it and never witnessed it. Jarod is also a young adult in the War of the Ancients trilogy so Maiev likely isn’t much older than he is. It’s a bit wonky because Blizzard seems to waver between wanting to retcon the Knaak stuff and wanting to keep it, so it tends to go back and forth and create this weird hybrid.
I will note that the kaldorei, all the kaldorei, loved Azshara, but anyone not a Highborne really disliked the Highborne themselves. This was to the extent that when the demons started demoning, the kaldorei, even Lord Ravencrest who was not Highborne and thus a political rival, were adamant that the Highborne must have taken Azshara captive and were doing all the evil of their own volition. None of them were on board with the ‘cleanse the world train’, they just couldn’t fathom their precious Light of Lights, whom many of them had never even seen, doing something so terrible.
It’s one reason Tyrande would need to be dragged kicking and screaming to any coronation, because she saw firsthand the damage venerating a ruler to the extent Azshara was could cause.
In terms of if ANY living kaldorei were around during the conquests, it’s again kind of nebulous. We don’t, for example, know how long it took for the immortality of the Well to take hold, kaldorei may have just lived gradually longer and longer lives until they stopped aging. We know Azshara wasn’t the first monarch, and there were those next in line, via the Princes, so at the very least one kaldorei generation did die of old age.
As usual, since we have no idea what the default age of elves is, and Blizzard keeps going back and forth on how old they get, we don’t know how many still lived. Between Azshara halting the expansion and the War of the Ancients was about 2k years, which is… a huge span of time. And so many kaldorei died in the War and then the Sundering, I don’t think anyone who even had parents that fought the trolls, or grandparents, would still be alive.
The biggest contender, that said, to have been alive during the expansion of the Empire would probably be Elisande, but she is dead fives times over.
