Hi,
I'm the creator of this engine and I want to answer your questions.
the Z index is the layer (or priority if you wants) not stretch or scalling.
The engine is optimized to load and display many sprites at the same time not just one
You can also made many scroll map with multi layer transparency.
On the documentation some function are noted "slow" but I mean "slower" (we talk about millisecond or microsecond

) than the basic function in the jo engine.
To answer the question , you can but you have to do the swap ticks or use a modchip, but one of my friend is working on it

.
PS: I will add a mode7 feature to the engine wednesday.