I'm in the midst of starting modpack dev for a new pack and am sorting out performance right now, but DH seems to be the only real issue I've noticed.
I'm using the C2ME forge port after trying the more updated fabric version via Connector with cpus variable in the properties to utilize my full CPU. There are a couple issues I've noticed despite better CPU numbers.
A. DH doesn't recognize C2ME, this isn't necessarily an issue, but I have noticed faster chunk ONLY if I'm near the border and LOD gen isn't particularly slow or fast using Aggressive or Extreme presets on Full.
B. Chunks near the player are entirely unrendered, but loaded, except for chunks with LODs pregenned. For whatever reason some don't, resulting in abnormal holes that never render. There's no real performance decrease related with these problems. My FPS is at 120 for testing, my TPS is stable and quite low, and my CPU is capping at 45% with LODs and chunks genning. It just seems that some chunks can't render for whatever reason.
I've not seen this issue before, and it translates to dimensions as well, causing massive generation times despite the fact that after initial lag the chunks and LODs begin to load normally.
I am using Tan's Huge Trees for testing it out reasons, but chunks with lots of trees have been genning fine while chunks that are just water, or water and trees, are not.
This is on Forge 4.7.13, DH 2.4.5, MC 1.20.1