My planning is usually limited to:
leaving today or tomorrow morning, after rush hour.
driving for 3 hours, more or less, at which time my back says it wants to go for a walk.
That usually coincides well with The Princess(Black Lab) wanting to walk, pee, swim and smell whatever.
Coffee and a snack, then back on the road and repeat.
Find suitable spot to settle in for the night.
Weather, water, whims, can alter any of the above plans.
Sometimes I search online for places of interest near where I am and allow GPS to take me to those.
I drive Highways until bored, then meander in the general direction I'm wanting to go on secondaries.
If I have no destination in mind, roads are chosen by whichever one promises to be more interesting. (that has convinced me to install a reserve fuel tank!)
Rarely do I drive after dark in towns, sometimes on highways if I haven't found a suitable place to overnight.