I don't really know where you hear mixed things from. I've only heard negative things.
No, you will have to do a lot of learning if you want to get a competitive job. You will learn some things that are relevant and a lot of stuff that is not at all relevant. It's pretty important that you know that successful people in the field are the ones that go out of their way to learn on their own time.
From my year, there are a lot of people willing to help when its cram time aka 1 hour to 1 day before assignments are due and tests are given. You do have time for extracurriculars if you stay on top of things.
Yes, you would be at a significant disadvantage compared to anyone at Waterloo. You can still compete with the students there, it's just that you should know that McMaster isn't really going to help you do that at all.
If you have a chance at Waterloo.. take it. To compare Waterloo and McMaster's software programs is like comparing highschool to middle school. You will have an easier time definitely if you come to McMaster but you will not be comparable at all to anyone who graduates from Waterloo if you put in no effort on your own.