Currently optimizing a modpack for 1.16.5, I have good fps, but exploring chunks causes it to stutter and get laggy.

For performance mods, I have Sodium Reforged, Starlight, AI improvements, and some other small fixes. I haven't used Optifine or Performant here due to their lack of open source and bugs with other mods, but I know Performant makes generating chunks a lot faster. Chunk Pregenerator is also very helpful but requires the player to wait like, a day to actually be able to play.

Servers would help, but they also cost money.

For JVM arguments I am using

-XX: UseG1GC -Xmx4G -Xms4G -Dsun.rmi.dgc.server.gcInterval=2147483646 -XX: UnlockExperimentalVMOptions -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M

I'll post my mods in the comments because Pastebin links are illegal in text posts.

Exploring is really important in this modpack, so I really would like players to be able to explore without it lagging so badly.