Different post offices handle the load differently. The "community" mail boxes really changed things
AFIK if you live somewhere established area that gets door to door, you get to the door delivery, if you have a NEW address, you get a community box. The post office is REALLY pushing the community boxes, they're a LOT easier.
Where I am now it's all rural routes... delivered by car/truck. There are 5-6 routes out of the local post office and they have 3 trucks... one of which is in the shop (they just got 2 new Dodge trucks). Carriers sort, then go do their route.
One morning my truck wouldn't start, so I did the route in my '84 Olds. NEVER AGAIN, nothing wrong with the car, but everybody wanted to talk about the car, I only got half the route done.
When I worked in Cooksville (old area, hardly any community boxes): carriers would do their sort, jump in a cab, drop half their load in a green box (so they didn't have to carry it all day) that was mid way in their route, then go start their route (the boxes aren't green anymore, they're that anti-graffiti motif, but we still called them green boxes)
Then there was the Matheson carrier "super" station. they centralized a bunch of carrier stations into one BIG station and they had a bus that would cart carriers around, but they stashed their load at a community box midway on the route, and circle around to it.... but their walk is much smaller because it's mostly delivering to community boxes.
At Matheson, which handled a lot of "business" mail, some of those businesses had a private contractor pick up and deliver their mail from the sort station.
Even within each post offices there can be major differences in routes. A friend worked up near Weston/Lawerence and there was one walk where EVERY address was a house with a mail box, every house had a porch with 4 or 5 steps. NO BODY wanted that walk, so my friend took it when she was in her 50's. She's retired now, and she's the healthiest 71 year old I know. (Dina was a fun lady. She used to show up at Mosport, with her 125 Honda racer STUFFED into the back seat of their Honda Civic,we'd put the bike together and then she'd go out and just KILL IT, well into her 60s)
So how they DO things is dependent on the topography/density of the delivery area. No singular "game plan"... just get the mail delivered, as cheaply and efficiently as you can.
One thing I found REALLY strange: up here on rural routes, the carrier is allowed to have a "helper", that gets the same pay rate, no mileage.
And up here, with rural routes: Amazon is killing the carriers. Sometimes half the load is Amazon packages, which is a different pay rate than Canada Post packages.
In MY experience, on rural routes (our routes were fairly high mileage) half your paycheck was mileage and yeah, it's not enough. My plan was to buy a KEI truck, but couldn't make the numbers work... so I don't do it anymore... it didn't help that my car/truck insurance company found out and threatened to cancel my insurance, till they found the insurance code in Ontario says delivering mail part time ISN'T commercial activity... full time YES, part time NO... and my insurance company wouldn't insure a KEI.
Canada Post sort boxes make real good storage for motorcycle parts. They have LIDS.