Why Pre-Generation Is Heavy
Generating chunks is CPU-intensive and writes many region files to disk. Running it on a busy server or a low-end machine can cause stutter for everyone playing. The goal is to let it work without ruining the experience.
Practical Steps
Run pre-generation when few players are online, or during a maintenance window. Lower the generator's speed or throttle setting if the mod offers one — a slower run spreads the load out and keeps the game responsive. Avoid flying around or triggering new chunk loads in the same area while it runs, since that competes for the same work.
On a server, make sure the world is on fast storage if possible, and avoid running other heavy tasks (large backups, world edits) at the same time. If players report lag, pause the generator, let 
things settle, then resume. Once the target area is fully generated, the ongoing cost drops to near zero, and exploration in that region becomes smooth because chunks are already on disk.
If you only need a small area, generate it in one short session rather than leaving a long job running unattended.
