On crimson and warped forsets: Nylium and wart blocks generate below the lava on lava lakes and below the bedrock on the ceiling from around Y=32 to Y=28 the terrain seems normal with only netherrack and magma. after Y=28 nylium (and rarely wart blocks) generate like in normal terrain.

On basalt delats: The basalt generating on the seiling is only 3 blocks thick. On java it can reach the bedrock of the seiling and can contain "blobs" of blackstone near that level. Also glowstone generates in the roof, something that isn't on java. "lava lake floor" generation is in full parity. 

On soul sand valleys: Glowstone also generates on the roof of the biome (like in a normal nether waste for example), something that has been removed from java.