I think its a good idea to split two 'usages' , as they have different solutions/options.
a) running/controlling/selecting patches
this requires no java, and communication can be done via midi etc.
so things like an iPad or any other control surface could work
b) editing/creating patches
you need a java environment, so that rules out an iPad, but presumably not android.
you also need to be able to compile that patch and upload it, not impossible on an android but may be slow, and take work.
touch screen should work, but there is no specific support, so like most applications its going to be like using a tablet i.e single touch , a bit 'mouse like' - but wont have multi touch or many gestures. (other than those supplied by the underlying OS).
to get such support would require someone develops it (Im not likely to get a surface any time soon, I don't know about johannes)
note: im also not sure of the current support in Java and Windows 10 of multi touch, but that will be something who plans to implement it to investigate
one final point, personally, Id say without explicit support, a touch screen might be a bit 'fiddly' in particular dragging the connections around which are pretty small, for touch screen you'd probably want something with smart 'connections' , and also an integrated zoom function. (the later may be part of the OS, so might already work)
anyway, just thoughts, would be interesting to hear from users than have tried... it may be Im being a bit too conservative, and it works fine as is.
btw @cube48 showed a nice video of SunVox working on a touch screen, which is not very different...
see this thread : http://community.axoloti.com/t/raspberry-pi-zero-axo-masterkeyboard-display/705/7