The only form of Creatine that uses different mechanism of action to increase phosphocreatine stores in skeletal muscles is Creatine Magnesium Chelate. The whole goal of supplementing creatine is to increase phosphocreatine stores, everything else besides MCC uses the same idea as monohydrate. Usually you hear about them being more effective, better absorption etc, but I don't see any clinically significant studies indicating they saturate your muscles more than what is possible. Ie if monohydrate works for you, the fancier version won't do anything extra regarding creatine levels if you reach saturation. They might have another health benefits (Ie nitrates in creatine nitrates), but in regards to your phosphocreatine stores, nope. People who don't respond to monohydrate usually have enzyme deficiencies, their muscles are already over saturated, etc, which is why MCC is a good idea.
Think of it this way:
We have 2 compartments, say say outside (outside the muscle) and inside (inside say a muscle). Creatine can travel to the inside of the muscle when it is outside through a layer (think a door way of some sort). Inside the muscle, phosphate trapping makes it so there is a lot more creatine on the outside than the inside, and the system wants it to be fairly equal, so creatine from the outside moves into the muscle. Ie imagine pushing a bunch of weight against a door, eventually you will go make it so there is a lot of force on the door and you'll go through the door. Once saturation is reached, the system always wants to be in equilibrium, so it shifts back and forth. So that's why over dosing creatine won't make a difference, the muscle can't get more in than what it's max storage is.
Now, how does this apply to those who don't see a difference with monohydrate? Creatine uses a protein (CrT), which is "energized" by outside sodium. If you have an issue with CrT (ie what I alluded to earlier with enzyme issues), you won't get any benefit from monohydrate.
In regards to the "fancier" creatines:
When creatine is inside now, it's not creatine anymore, it's called phosphocreatine. Because it's now not creatine like it was before it went inside, it means the outside will always have more creatine than the inside, so you can keep getting creatine from the outside going into the inside (if there is space), trying to reach equilibrium.