When I do a longer ride (which isn't all that long now!) I'll be out on a 3 lane highway each way. There is a good shoulder and rarely a car parked (only if they have car trouble). But even so, since I ride at night when traffic is light, I'll still move over into the car lane, constantly using the mirror on my glasses to make sure nothing is coming up behind me. I do it because the more time you spend on the shoulder, the more likely you are to get a flat since all the trash tends to get pushed to the side. The shoulder also isn't always as smooth as the regular lane.
But if I just ride in the neighborhood, there are plenty of cars parked on the street and I try to stay well away from them. Fortunately, again because I ride at night, there is little traffic. Even less since I'm not on the highway.
I used to ride from my home near Pearl Harbor to Waikiki (over 12 miles). When I was riding during the day, there were long stretches with no bike path and sometimes not even a useful shoulder. Hated that in traffic so I'd always push as hard as I could to get past those stretches as quickly as possible.
I don't know about you, but I love having a mirror attached to my glasses. For one thing, it is far more stable when riding to look in a mirror than it is to turn your head to look behind. And at my age, with arthritis in my neck, I can't turn around that well anyway. Also, if I do turn around, I'm no longer looking through my glasses - I'm looking more to the outside of the glasses so things aren't all that clear. But with the mirror, I'm looking at it through the glasses. A mirror on the handlebars bounces around too much!
I also found that it doesn't pay to buy cheap headlights. Not just because they are not as bright as the better ones, but the mounts always break far too soon. You can get a good NiteRider light on Amazon for under $100 and you'll save money because the cheap $40 ones will break so often that they end up costing more.
I also always have three tail lights. One on the back of my helmet and one sitting right below my seat. There are two reasons. One is that I noticed from seeing other cyclists, that 2 or more lights just get your attention better. Another is that it is almost impossible for all 3 light to die out or fail at the same time and, being behind you, you probably wouldn't know until you finished your ride.