I'm hopping into Chaos myself with the headliner of 2020: Nurgle
While the GUO benefited the least from the changes (he could already shoot into combat for example), there are changes worth looking at stuff over:
+Morale punishes us less than it used to if it goes south (though I appreciate Sloppity Bilepiper's morale gimmick enough to want to run him just to get daemons back more often).
+All the non GUO Greater Daemons with shooting attack options can use those in melee, which helps them reap chaffe easier (also it buffed Rotigus who couldn't shoot into melee before).
+Since heralds no longer share slots for some reason it's cheap to buy into multiple detachements if we want to maximize our support buffs (I can see double patrols being popular for this as it means 4 HQs and 2 Troop Choices for 2CP, quite a decent steal honestly)
+Units we charge with FLY no longer get to shoot for free if they escape combat
+Furies have plastic models thanks to Warcry and honestly might be worth looking at as a cheap flying screen unit.
+Skull Cannons, Burning Chariots, and Soul Grinders (all models with heavy weapon shooting attacks) got better thanks to how heavy weapons work in 9th.
+Feculant Gnarlmaws are improved because the new detachment system makes taking them worth doing.
So I've seen some complaints online that Nurgle is too slow for this edition and I had to scratch my head a bit. Unsupported, sure, but Spoilpox makes them movement 6", the trees let them run and charge, With that you're looking at a 24" threat range on a smaller board. Nurgle is more of a "go second" army, but it's worth doing so just to have charge targets (unless you're just running a list that fills the board with Nurglings before your opponent can move, then you may want to go first).
Plus your opponent will be trying to move forward to engage with you, so you'll both be hitting the mid field and then grinding from there, and grinding is something Nurgle still excels at.
I think one of Nurgle's better changes is the ability to toss the -1 to hit around at different targets. Like the GUO who previously didn't need it, instead of the Plaguebearers who tap into it naturally when over 20 models.
Long story short, I feel like the army has tools under its belt to work better this edition, even if it has to worry a little bit about blasts (I'd worry mainly about missile launcher heavy weapon teams or Devastators to be honest, since they throw so many dice on a cheap firing platform, and not the internet's new boogeyman the Wyvern since that only averages 4 Plaguebearers killed in a single shooting phase).