If I create a world with any seed, then find a structure (something that can be found with /locate structure) or decorator (something that you can't find with /locate) and then create another world with the number 4294967296 (2^32) added to the seed of the original world, then the structure and decorator locations will have the exact same x and z coordinates, the y coordinate of the mineschaft is also affected, but it is possible that the y coordinate of the ruined portals and decorators are not affected. Even the shape of the structure and the loot in the chests are the same, but not necessarily the enchantments. 

Steps to reproduce:

1. Create a world.
2. Find a structure or decorator
3. Remember the coordinates of its location.
4. Create another world with the seed of the original world + the number 4294967296 added to it.
5. Go to the coordinates of the structure or decorator in the other world.

Observed results:

The same feature is in the same location. Even the shape of the structure and the loot are the same, but the enchantments possibly aren't.

Also, if you find an amethyst geode, the shape of the geode and the positions of the budded amethyst blocks are identical.

Lava pools are also identical. 

Villages generate in the same locations in worlds with seeds differing with 2^32 as long as there is the right biome. If one of the villages is abandoned, then the other one will be too. The shape of the village depends on the biome. 

Ores sometimes generate identically, sometimes just the shape of them is the same and sometimes they are different. 

Dungeons are affected to some extent. 

It is likely that other things that I didn't list  are affected

Expected results: 

All elements of a world should be unique for all 2^64 seeds. 

Notes: Ruined portals and mineshafts are easier to test, because they generate in every biome. The same glitch affects some caves, decorators (features), the nether and the end. MCPE-154333 , MCPE-155137, MCPE-154947, MCPE-156090