So from the description side all sounded very great and perfect and so I ordered my device for my iPad Mini (gen 7). I must say after some testing my feeling are very sobering. Here why:
Like mentioned I used an iPad Mini for my testing as my Android tablet is very very old (Huawei Media Pad with only 64GB of space). First I tested my usual games to find out that if the game doesn't support controllers you are very fucked up on iPad. The the onscreen mapping simply doesn't exist here.
So I was looking for games supporting controller and ended up with Diablo Immortal and Titan Quest with OpenTyrian for the future.
First of all Diablo Immortal works so far so well with the controller as long as you play your character, As soon as you need to move trough the menu or change your skills, your equipment and so on you can forget it. You automatically swap back to the touch screen as it is easier to handle. But on the game site, for moving your char it's great. I just don't understand why they put the B button for fighting and the A for interacting but at least you can swap them in the game settings.
Moving over to Titan Quest it was a totally different experience. Why? Well the game is more build for controller and it swaps to a specific interface for it. You can always use the touch screen and as soon as you move again with the controller it simply swaps to that interface. I must say till now I had much fun with it.
The third game I wanted to test was OpenTyrian but unfortunately there is an existing bug that let the controller not move one step forward in the menu but 2 - this isn't the case when testing with my iPhone but that wasn't the goal for this controller.
I also tested some racing games like Asphalt but racing games are nothing for me. The next wall is always mine lol 
Than I wanted to adapted the told possible to edit additional buttons at the back as example. Boah I was so disappointed. I wanted as example for my games to map the letter m from the keyboard to the M1 button - but no - this is not possible. You can map it to some buttons but not free to what ever you want... I don't know yet but maybe also an iPad restriction?