Your salary is probably going to be lower in Montreal, but it's much cheaper city to live in than Vancouver or Toronto. There are high paying jobs if you know where to find them, but it seems to me like a lot of the software engineers I've come across here are a little less "ambitious" and don't mind settling for a smaller salary if it means more stability. It's also very taboo here to talk about your salary (sometimes even to your SO?) but that's changing and I think it's not unique to Quebec at all.

In my experience, and purely anecdotally, I've really witnessed a 2 speeds system where some people are very highly paid (120k+, keep in mind you can buy a condo in the middle of downtown for 300k) and some are getting very (40-50k) low salaries for the same amount of experience, same alma matter and probably even the same skill . How you sell yourself is always a huge factor in how much you get paid, sure, but the difference is particularly striking in Montreal imo.

As for seniority, most of the teams I've seen are very young with very dynamic leads. The industry is booming right now ( or was booming before march, I'm not sure now).