The classic definition of RPG, derived from table top games, is a game where you assume a character, and interact with other players or the environment as that character. This can be either a character you created from scratch, or a pregenerated character put together by the Game Master. In an earlier post, you tried to distinguish between role-playing and play-acting, but there’s no distinction there. Role-playing is play-acting.
The other thing that RPGs introduced around this time was the concept of “leveling up,” where the more you played a specific character, the more powerful that character became.
When they started making RPGs for computers, it was really, really hard to code complex interpersonal interactions. But it was relatively easy to write systems where characters became more powerful as the game progressed, so early RPGs focused instead on the leveling up aspect. In those early RPGs, your characters usually had no personality at all, and nothing you did could really affect how the story unfolded. Player choice mattered in terms of figuring out combat tactics and optimal build strategies, but the game would always end with The Heroes fighting the Evil Dragon and saving Fantasylandia, or whatever.
By the 90s, that started changing. Games like Baldur’s Gate started including complicated, branching dialogue trees where your responses could effect how the plot proceeded. The player was given some agency in determining what sort of person his character was, and that personality mattered. This was much closer to the original meaning of “RPG” - you could say, “My role in this playthrough is an honorable paladin, my role in the next playthrough will be an evil wizard,” and the experience of playing the game would be noticeably different in each playthrough.
“Open world” simply means that the game allows you to go to (almost) any part of the setting whenever you want, instead of presenting content in a linear series of stages.
The Witcher 3 is widely held to be one of the best open world RPGs ever made. I’m personally not that big a fan of it - while the writing and world-building are top-notch, I really struggle with the combat system, making the experience more frustrating than anything else. But whether or not it’s an RPG or open-world really is not a matter of opinion. If you say you don’t think it’s an RPG, people are going to look at you funny. Like this: :dubious: