On a scale from 0-100 where 0 is Mario Kart and 100 is real life, I’d put Horizon at around 75. It’s mostly realistic, but is intentionally forgiving in certain aspects.

As for solo, if you’re looking for a good story, you’re probably going to be disappointed. The game nowadays is mostly focused on collecting cars and the online experience (mostly racing). You could (and probably would) enjoy exploring Japan for a while, but if you’re not into racing I think you’d burn out pretty quickly