I actually struggle with Monza. I always mess up the braking zone into Parabolica and end up in the gravel.
Monza looks easy because it has a limited amount of corners and long straights. However to nail a good lap you can't make any mistakes in braking, turning points, corner speeds and accelerating. Very demanding if you are looking to set the perfect lap.
I'd def throw in my vote for Montreal as the corners are easy sweeping ones, plus the AI is rubbish there, making it an easy win. Monza is easy too, but in terms of beating the AI, its not as easy, especially as the 2nd chicane does take some effort before you're really fast. I'd also like to say that a track like Monaco may seem daunting at first, once you've got the hang of it, it's an easy win ever time!