I just tried the simplest implementation on v100.10 of an updating view following a graphic object and the transition is totally smooth. As the number of updating graphics increases however (to around 200 graphics updated every 100ms together with the SetView update) I can see the flashing effect you mention. I would not consider that a bug, but simply a performance limit. I used simple markers, maybe with other graphic types or labels like you use the performance is worst and it may be considered a bug.
Concerning adding graphics or updating geometry I do not know, I would just try both and see. The good thing about updating the whole graphics is that you can update them in parallel and then add them as a range which is usually faster.
Note: I am not a runtime specialist or anything, just giving my advice based on the little I know.