Interesting. I'm not sure that things would have turned out all that differently. Chamberlain, who is considered a weak appeaser , had finally drawn a line in the sand, and had issued a guarantee of Poland's borders, which Hitler ignored.

Hitler's actions and initial successes really discredited Chamberlain and any isolationist at that time.

If Edward had been king, could he have organized opposition to the guarantee or the war that followed? I'm not sure. Hitler was going to have war with someone and that was that.
However...
I have read some arguments (not just by that nut Buchanan whistle )that Hitler didn't necessarily want war with the UK, seeing them as suitably Nordic cousins. So MAYBE if Edward had been King, he could have prevailed on Chamberlain not to issue such a guarantee to Poland, but it's a REALLY REALLY long shot. Churchill said that "The [German] is always at your throat or at your feet", which is a sentiment I think Hitler would have agreed with though obviously they would have different preferences..

So ultimately, no, I don't think Edward as King would have made the difference. Hitler was just bent on war, domination, extermination and conquest. He had a BIG problem with the word "no", which sooner or later even the most submissive British government would have had to tell him.

"When the snows fall and the white winds blow, the lone wolf dies but the pack survives."
Winter is Coming

Now this is the Law of the Jungle—as old and as true as the sky; And the wolf that shall keep it may prosper, but the wolf that shall break it must die.
As the creeper that girdles the tree-trunk, the Law runneth forward and back; For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack.