Seeking advice about how much time to take for layovers

I am looking to travel Ottawa-Krakow this summer, but cheapest options i can find are with two transfers (e.g. one in canada + one somewhere in europe). However I see layovers between 1 to 6 hours, and not sure how much time I actually need.

I know that entering schengen zone from Canada I would have to go through passport control, which takes time. How about when returning back? Will I need just as much time, or is it handled in first airport I arrive to in Canada?

Also, I have heard that sometimes you are required to get your checked baggage and go through security again when you return to Canada?

My options are YUL/YYZ airports in Canada, and one of CDG,MUC,FRA. I would appreciate if people who travelled there in similar situations can help me estimate the time needed, thanks!