What are your goals? so far you have only asked whether it’s possible to do this whole world splitting thing.
The main reason why I asked was because I wanted to know if it was possible, and if so how easy it would be to do it. If it was going to be easy to do, and would have benefits, I planned on doing it. However, the answer thus far is that it would be too difficult to implement and I would not see any noticeable difference and it could actually cause worse performance.
As you said, if I planned on putting these ‘regions’ on different servers, it would have a greater benefit since Bungeecord could balance the load. And while down the line this could still be an option, I think that right now my best choice is to just create one large world.
One way that I may have to do this is by stitching the worlds together. My world painter struggles with creating the world, since it is so large (400,000 x 400,000). So I have been looking into being able to stitch smaller parts of it together. However, while I have not looked very thoroughly into this process, it does seem rather difficult, but possible.
My ‘goals’ were to modify the server plugins for each region, so that they each behaved differently. For example, I planned to modify some of the entities in the game, so being able to use a sheep as a sheep in one region, but being able to make it something else in another region was appealing. (Animals would not be able to cross regions) However, this is honestly not that big of a deal breaker, and I can still work within the bounds of minecraft for the server. (I considered a modded client, but plugins just seem so much easier)
Again, my ‘goals’ were not deal breakers, just I was thinking about them with the idea of dividing the world into different regions. Now, I will just have to do the same thing while working with one large world instead. It should not be too difficult, since there are plenty of other servers who manage to do this.
Thank you to everyone for your help and comments, I really do appreciate it! I got the answer I needed, and I am grateful for everyone’s time.