Hi!
You probably want to use the procedural mesh component and make voxels for your procedural terrain. You could go cubic like minecraft or use smooth them out like 7 days to die.
You’ll probably want to split the generation into chunks of voxels so you can generate and update voxels in batches. You can use various noise algorithms to determine whether each voxel is air or solid, and whether solid voxels are stone, dirt, whatever.
You’ll need to heavily optimize as much as you can.