szymek resumed it kind of nicely, while searching on the forums can end up showing canvas+ as a bad option for android, the situation changed after they got depreciated, that is of course if you are not using any feature that is incompatible with it (form controls and the XML plugin mainly If I recall correctly), however try to ask some people with different devices to test, I know canvas+ can be problematic on some systems.
Crosswalk was really nice and worked great until the chromium base (which it is based on) got its update which broke V-sync completely and never get back to its original smooth point. Audio however I am not sure, I think I remembered that crosswalk has a specific support for audio.
it seems that each time a solution is becoming the official one, it gets issues, but when it is not anymore, it becomes better, but that is me assuming that there are spirits playing with the texture of reality, in the end, try the different options availiable, as none are directly supported by scirra.
for IAP, I am not sure hiw that works though.
Game design is all about decomposing the core of your game so it becomes simple instructions.