The tenth anniversary seed (celebrationmk10) is made out to be easier than a normal world when you look at the wiki with the only listed changes being that chests give you items of the best modifier and the world is painted (Also you start with different NPCS) However there are many more changes, so here are the ones I’ve experienced so far. The shimmer is much more common, you spawn on the beach rather than the middle of the world, living trees are super common and on large worlds border each biome except the beach and the forest, king slime with get smaller as you chip his health away, The Eye of Cthulhu is significantly smaller, the brain of Cthulhu is a little bigger than the player and the creepers are super tiny, and lastly pink bouncy boulders exist instead of normal ones and are pretty much insta death in early pre hardmode.