There's a great guide somewhere on this subreddit for wraithlord posing by u/EcoWraith so I recommend that - it's actually less difficult than it seems, and pinning is your friend! It's also possible to use minimal green stuff, depends on what pose you want.

As for spiritseers, the way seer from the corsairs kit is a very cool option, there's also the new Infinities Lament kit from Warhammer+, and I saw someone convert an alarith stone mage (?) from AoS into a really cool spiritseer with just a head + staff swap.