Welcome to the Ghost Halls!
A lot of the Wraith options are strong-- your biggest challenge will be rounding out a list against horde armies, and not over-optimizing against Elite/vehicle armies (which is easy for Wraiths to do, accidentally.)
You're paying for a tougher, more expensive war-walker that can counter-charge deepstriking units. As Iyanden, you'll never have to worry about the degrading profile, which makes taking multiples way more useful.
The big downside of Wraithlords is how easy it is to tar-pit them in melee, so you'll want to keep them safe from cheap, high-model count infantry that can tie them up.
My favorite loadout is just 2x Catapults & 2x Shuriken Cannons. That gives you 10 shuriken shots with the promise of spiritseer rerolls. The sword is helpful if you need to punch at T4+, but depending on your list, you just may not need them. (I've ended up dropping mine for more heavy weapons to up my overall shot count.)
I'm probably in the minority here, but I've found that Flamers aren't worth it on Wraithlords. They're expensive (almost the cost of 2 shuriken cannons), and don't really help the Wraithlord's vulnerability to getting tar-pitted because of how pile-in moves can be abused in 8th. You'll find that opponents who know what they're doing will declare a charge against another unit with their blob, then pile in 3" into your Wraithlord to dodge the overwatch on the flamers.
Wraithblades (Axes vs. Swords):
Both are good, but I agree with Partninja: The swords are 50pts cheaper and better against hordes. In fact, blades with swords & a wave serpent is the best, fluffy anti-horde option that a Wraith army has access to.
The axes are more well rounded, and can reliably assault vehicles & monsters-- but those are the same targets that Wraithcannons are already perfect for hunting down.
Wraithguard (Cannons vs. D-Scythes):
You can't go wrong with either choice. The Wraithcannon guard are tanky, upcosted fire dragons. Keeping 5-6 in Webway strike is awesome, and will completely change how your opponent deploys.
Since the codex drop, D-scythes have become way less swingy. You can pretty much always expect to get between 8-12 auto-hits. Not quite as effective vs. vehicles as the Wraithcannons, but decent at anti-infantry and anti-horde too. Probably the most well rounded Wraith unit. Kind of a tossup between these and Sword Wraithblades for the best mainstay of a wraith army.
Despite them being flame templates, they're way less vulnerable to the overwatch-skipping pile-in abuse that the Wraithlord is thanks to their ability to backpedal out of melee and shoot.
Overall, like Partninja said- Wraiths are good in any Craftworld, and you don't really need to be Iyanden to make a Wraith army. If you're looking to double-down on the benefits of Iyanden speceifically: Wraithlords and Wraithblades get the biggest benefit from being Iyanden, while D-scythes get no benefit at all- so it's up to your playstyle.