I mean, you can technically use multithreading with Parallel Lua, but as far as I know Roblox doesn’t internally use multithreading, (I’m pretty sure they use parallelization for rendering though, there’d be a lot of artifacts if a pixel was colored one at a time).
The only reason I mentioned StreamingEnabled was because of it’s mesh LoD feature and how it unloads things in chunks far enough away from the player. It was a simple solution, and I’m pretty sure a world chunking system could also fix this issue.