I've wondered about this - first thoughts are to stay off the A roads, but visibility tends to be better on A roads as they're straighter and with shallower curves, and fairly regularly you'll go through civilisation lit by street lamps. Side roads/lanes may be quieter but then no-one will be expecting to see a bike and might be on top of you much more quickly. Guess it depends on the roads, but often you won't know until you get there. My scariest experience on a bike was bendy country roads shrouded by trees, very dark and visibility around corners was often very short, I dreaded the sound of an engine coming up behind me.
If a driver is paying attention, you're arguably more visible lit up at night than in the daytime, but they never seem to be able to pass you as sensibly though.
I generally prefer the dark quiet lanes - I love the peace - tend to think you are more visible on these as your lights really stand out. Of course you could be unfortunate enough to encounter a total nutjob but that could happen anywhere. With cycletravels routing I can often ride all night hardly encountering a car, especially true I think in these cursed times.
With regard to visibility and bends, maybe your lights aren't good enough. I find a GPS with a map is particularly useful at night as you can see the bends coming up on the map.
I never go too fast at night anyway - I'm in it for the long haul, all night, and so it's particularly important to pace myself. Can always speed up as dawn approaches. And you do of course have to pay particular attention to the surface, particularly downhill - I never let the bike go on night downhills - the extra braking this entails means that you do of course have to check your blocks closely before setting off, particularly if it's wet.
Anywhere there are streetlamps I switch the headlight off, or at least switch to low output, in order to lenghen battery run-time for high power usage. I always also have a front flasher. And two rears.