(1) Only 3 of the original 7 elves are (ahem) fleshed-out
Viridia was a proud warrior who got corrupted by Scrome, but Merigall likes them evil so he wants her just as she is. Either way, she's in a sword and she's making people kill people.
Algared decided "OK, I'm going to give this whole Elvenspring thing a go" and he still hopes that can happen. It's not his fault that his descendants got undeaded. He's in a sceptre which is pretty handy, if a tad debilitating.
Iridne said "orcs are good and I'll prove it to you" and she's now helping orcs. Hooray for her. Her cloak clasp is amazing.
The Shardmaiden shattered herself into a thousand pieces. Fine.
(2) There is no reason to worry about the remaining three
The other three remaining really early elves? Stanengist needs to have the three rubies of Gemelda, Neyd and Nebulos so it can automatically dispel magic. (Is this good? It feels like this would also dispel friendly magic cast near the wearer of the crown.) But there's no indication of what they'd do if you plucked them out of the crown, or how their personalities are different (even though that's supposed to be one of the things about Stanengist: that it contains multiple conflicting personalities).
This is especially weird as Gemelda is said to be the wisest and the founder of the Redrunners (so you'd have thought that Kalman Rodenfell would want to make sure that Gemelda wasn't one of the elves sacrificed as part of sealing the rift), Nebulos is explicitly mentioned as the one who created the Stillmist, and Neyd is the amazing gardener who made rivers work. These sound a lot more interesting than the other elves!
Stanengist also needs an additional ruby so it can send someone demonic or demon-adjacent slightly mad, or seal the rift. But the difference between "you must find Stanengist (contains 3 elf rubies) and an ancient elf ruby" vs "you must find Stanengist and an ancient elf ruby" isn't clear to me narratively.
And when it comes to the choice of which rubies to add to Stanengist to close the rift, it's pretty much down to whether the PCs want to piss off Merigall by sacrificing Viridia, whose stone is the most annoying, or whether they choose Algared, who will Break most PCs by the end of the day.