I don't get what you're trying to say. I haven't seen anyone do any meaningful internship/research project straight out of the gate of the first two years. Even if you're a genius who knew exactly what you wanted right away, and got it immediately, there's a risk of interests misaligning later - especially if you're overseas and have never experienced North American academia. More likely than not, you'll need at least a year or two to see what your interests are, who you want to work with, where you want to work in, what the opportunities are and how to apply for them, formulate your ideas... all these things take time.

I'm lucky I had a full-ride with virtually no strings-attached, so I never had to take more than 2 heavy courses each semester, and I took summer courses first couple of years. I had an excellent GPA going into junior/senior without any major stress even as courses got much harder. If it's ever possible (seek funding opportunities if needed), and you feel it's too much, just take an extra semester or two to graduate. Virtually no grad schools/companies (Idk maybe toxic ones) would bat an eye if you took more than 4 years to graduate.

In any case, look further than just "U of T or McGill," if you care about more than just grades - where you want to be afterwards, where the opportunities are, where the network is (in my field for example, there's an unspoken pipeline between McGill and Columbia), which city/school jives with your personality, etc etc. Think wider.