My current primary PC is a technomancer who uses personafix CFs quite extensively. For ease of mechanics, and for his own piece of mind, the GM required that I take the Double Agent quality from Runner's Companion at full value (allowing the TM to have conscious, fluid control of swapping between 'softs... otherwise the program runtime and coded limits would run their normal preprogramed course with no 'out').
I don't know if using such would have an automatic effect on such deep-held aspects such as stream, but it wouldn't be unreasonable to think that their persona and/or specifics of sprite appearance could change. That was something that my PC did ahead of time as part of the personasoft CF, so I haven't really thought much about it outside of how it applied to that PC.
