Side Scroller, Natural Generation Block World

I wanna re-create one of my old VB games in UE4, making it 3D from 2D. I wanna create Infinite Generating Blocky Worlds like Minecraft, but 2D Aspects like Terraria. not just that: but there would be Layers.
Grass on the top,
Dirt next,
Stone after, with Caves.
deep underground Caves,
Hell.

also to note, Clouds can spawn in the sky too, Ores can Spawn in Stone, and Biomes too, and it is all like you’d Expect from Terraria.

I need severe help with this, as I tried making one 3D World that Generates overtime as a Test, but that causes lag from the Actor Class. if you can help me, please do.

-Many Thanks