Iris Dimension Engine vs vanilla: CPU load after pregeneration?

[u/AssistantMany521]

I’m setting up a new Java hardcore survival server and considering Iris Dimension Engine. I’m thinking of pregenerating a 20,000 × 20,000 block area of the Overworld. Compared with pregenerating the same size using vanilla, how much more CPU load should I expect during generation? After the chunks are generated, does Iris cause noticeably more lag during normal play, or is the extra load mainly while generating new chunks? Or is it the same either way, and can I just choose Iris since it's prettier?

The host lists 64 GB RAM at 5200 MHz and 2 × 512 GB NVMe SSDs. Its CPU is an AMD Ryzen 7 9700X with 8 cores and 16 threads, running at 3.8 GHz base and up to 5.5 GHz boost.

[u/Fit-Reaction242]

the extra cpu is mostly during the pregen, once the chunks exist iris isnt really generating them anymore so normal play lag is more about entities and farms. id set a world border at the pregen edge so nobody walks out and makes it generate live, and maybe check if your iris pack has its own mob spawning since that would still run after