Why do you want 6 layers if then you need to finger drum on a touchpad?
I have the impression that you are paying more attention to specs than to the realities of finger drumming. As others have said before, the feeling of a realistic drum needs to come from your fingers first and no amount of layers will help you (in fact, more layers are likely to make satisfactory finger drumming more demanding).
Also, I doubt listeners not caring about seeing a finger drummer instead of a real drummer will even notice whether there are 4, 6, 12 or 256 layers.
My advice is: pick any of the suggestions above and start finger drumming. If and when you hit a limit, optionally sell your device (second hand market works decently) and get another one with whatever specific it was that you, your band/peers or your audience missed. If that times comes, you’ll get great advice at Elektronauts about what to try next. 
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