A Royal Rom-Com
"William & Kate" is a look at the romance of William and Kate from when William went to St. Andrews for university and they met.
"William & Kate" starts with a scene featuring Prince Charles and Prince William walking along a path at St. Andrew's university on his first day with both Nico Evers-Swindell and Ben Cross looking like they were struggling to control their laughter at the terrible dialogue they were trying to deliver. It quickly lowers your expectations and so it goes on with further scenes which make you wonder whether you were groaning louder than the actors would have been at the end of a take. The thing I don't think it is genuinely possible to make a serious movie about William & Kate just yet and they shouldn't have tried.
As such the longer this goes on the more it becomes more like they tried to turn "William & Kate" in to a romantic comedy as we are meant to smile at a variety of things. We are meant to smile at the awkwardness of Kate trying to chat to William only for it to sound contrived when she mentions that they must have missed each other when they were both on a building project abroad somewhere. And we are meant to laugh at all the girls swooning all over William. I could go on because unfortunately "William & Kate" ends up indescribably forced. It is why it ends up much more romantic comedy than romantic true life drama.
As for how much fact and fiction there is in "William & Kate" in truth I haven't a clue as I never followed the Royal relationship that closely. But I get a feeling that you should take what happens in this movie with a huge pinch of salt as it all seems to painfully contrived, especially the dialogue. You should also try to get it out of your head that in this William sounds like Hugh Grant.
What this all boils down to is that "William & Kate" is hard work and comes across like a really poor romantic comedy which doesn't actually make you laugh but groan with all the forced acting and forced dialogue. Having said that I am sure if I watched this after a few I might actually find it fun as a romantic comedy.