From reading it seems that King Edwards never has any interest in conquest of Scotland. His my goal was the Welch land and dealing with France. The movie falsely starts out during a period of English conquest of Scotland as Wallace is a boy. This was false since a young Wallace grew up in peaceful kingdom of Scotland free of England.
However, after the Scottish king dies. Several competing parties to the thrown wanted power and nobody could decide what to do. So they invented King Edwards to mediate the affairs. It was then that he realized that he could easily take advantage of the situation by selecting a puppet king.
Anyways, Edwards was ruthless, shrewd and cunning. His grandson seems to be a chip off the old block.
If I remember it was King Edwards who expelled the JEWS out of England and they did not return for over 300 yrs.