Okay, this is my take on UE's;

The situation can be likened to that of games, in a way.

Apple devices are like well done 3rd person shooters, very colourful, packed with action and fluid in motion. The theme is a kind of pipe run but so well crafted it takes a while to notice it; all goes well if you need to do the usual tasks 90% of people require.
On the other hand, if you want to do something SteveJ and his merry men did not anticipate you'll run into the pipe wall and it is pretty much impossible to escape from that.
The experience might be pleasing in the beginning, but it limits your creativity a lot and makes users adapt to the machine instead of other way around.

WP devices on the other hand aim to be 3rd person shooter pipe runs, but often fail spectacularily.
You might be able to manage for a while, and then you find that when you should scale a wall suddenly your hands drop off. Or you are just about to face the boss-enemy, and at that instant your machinegun mysteriously turns into a tuba! And the boxes of ammo you find turn out to be chokolate candies...

Open devices on the other hand fall into totally different game category; they are more akin to games like MInecraft. Depending on the vendor they might include ready-made parts that fit together nicely like lego bricks, or all you might get is a huge pile of differently shaped parts that have nothing in common.
However in both cases you fortunately have glue! Several kinds of glue in fact, that comes with different colours; some of it sticky and some of it hard.
And boy you can glue anything together and make all your heart desires!
The end result might not be pretty, and it might not be like anything somebody else made into their devices but it works like a charm!
There's no limitation of your creativity, you can do anything you like.