For me, I put RPGs into two different categories.
We have Hard RPG and Light RPG.
What I mean by this, is a Hard RPG will allow for complete control over character customisation, allow for the player to essentially make their own story in the game. It's like how I consider New Vegas to be a hard RPG because I can make my character be who ever I want them to be, and create my stories with the material provided. Essentially, I'm making somewhat a novel with paragraphs already written out for me, I'm just putting them in to create a story.
A light RPG is a game which features one or the other. An example is Witcher 3, my character is pre-written for me, but I can make my own stories with that character, essentially Witcher 3 is more in line with the adventure genre, but has enough RPG elements for me to call it a light RPG.
I will also somewhat put Fallout 4 is this category, to an extent, you can create your character, but there's just a pre-written idea for you. You can go off on your own adventure and stuff, but again, I consider this more of an adventure game.
Here, I will also put in Final Fantasy games. But again, they feel more like adventure games.
RPG and adventure are very similar thinking about it, Light RPG is closer to Adventure than anything else. Really anything which falls under the RPG/Adventure label can be considered a Light RPG.