On a friday during rush hour, if you take the massey tunnel anytime around 5 its going to hurt real bad. I've had decent luck with the new SFPR.
Reservations I'd recommend only if you can get to the ferries minimum 30 mins before the sailing or else theyre void.
Coming back on the Sunday we've usually been ok for the 5 or 7pm, but you can always look up current wait times on the website:
Traffic at our Major Terminals | BC Ferries - British Columbia Ferry Services Inc.
If it's a long weekend its usually worse.