I mean... Slice of life is known to be plot-lite, and the road trip part could definitely fit under that label by the sounds of it. Depending on the tone I've seen stuff like this called "cosy" as well, "slow burn" might also fit technically and isn't restricted to one genre (if both romances and Dracula can be slow burns, that's a pretty wide scope).
I've seen what you're describing more in games, like Stray (the cat game, not the other one), Outer Wilds and the like, maybe look into how they're described to see if something fits what you're looking for?