Those wither skeletons are from a datapack called incedium that provides our custom nether. The higher difficult mobs exist to provide a challenge for the players and an enjoyable adventure. It is also a way to get the player to make a strategy on how he can kill those mobs (hint: maybe going above them can help you)

Hello, it would me much easier for us if you made a support ticket on our discord server and asked about these things there: https://discord.com/invite/earthmc
If you are unable we will take a look at your towns and respond when we have time