Hey,
I was there last year and the biggest IEM sections from what I saw and remember were from Letshuoer, Campfire and Moondrop. I also listened to some Final IEMs, and some Collab IEMs by Astell&Kern. Sennheiser had their IEM lineup as well.
Looking at the brand register this year, 64 Audio, Campfire, Final, Kinera, Shenzhenaudio (Moondrop) and Sennheiser are probably the ones you wanna look out for.
Other companies like Hiby, Shanling and iFi might have some IEM's to test their gear with too, but I dont remember that from last year. Who knows.
In general, just take your time looking at everything, have patience and don't be shy, people are usually very nice