If you want remove a vanilla biome from the spawn to add you custom biome,you should set the "biome weight" to high,and change the biome temperature to be similar of the plains biome,and finally,when you start a world, you spawn in custom biome.
If you want "delete" all vanilla biomes in the overworld to replace them all with you custom biomes,do it the same of last step with all you biomes,set a high biome weight for all you biomes,and change the biome temperature deppending on the biome that you want replace,this is for organize the biomes like vanilla as
-sorry for my bad english,is not my main language.
If you want remove a vanilla biome from the spawn to add you custom biome,you should set the "biome weight" to high,and change the biome temperature to be similar of the plains biome,and finally,when you start a world, you spawn in custom biome.
If you want "delete" all vanilla biomes in the overworld to replace them all with you custom biomes,do it the same of last step with all you biomes,set a high biome weight for all you biomes,and change the biome temperature deppending on the biome that you want replace,this is for organize the biomes like vanilla as
-sorry for my bad english,is not my main language.