I do not recommend editing arp patterns on-the-fly [i.e., while performing] either via sysex or via preset/patch editing software. Yes, both can be done, but so far as I can tell, each individual change to the arp pattern [i.e., each step] might be written to limited-lifecycle memory.
For performance oriented editing of preset parameters on-the-fly, I am planning to use the preset edit buffer just to be on the safe side.
Steve