Q1: I tested with more than 200 scenes, and any over 200 just would not load into the TW5 construction Scene tab. Got a pop up message I believe saying 200 is maximuim.
Q2: Easypano told me they can program the software to handle more than 200 scenes, but for a custom programming price. Price is not that significant... but if you are interested, suggest you trouble ticket to them to get your own quote.
Q3: I have not worked with other virtual tour construction software, so can't answer your last question.
Hope this helps!