The Stone Biomes mod replaces almost all the biomes in Minecraft BE with stone ones. Blocks of land will become a rare occurrence in the game. Well, actually, like growing trees. Wherever you look at Minecraft Bedrock, you will find only stone textures. Blocks such as granite or diorite will be found just as often.
Stone Biomes mod does not affect any structures in MCPE. They will also be generated in the game. Monsters will spawn in the MCPE in the same quantities. But the animals will be slightly smaller. But do not despair, there are places where you can find land.