Has anyone ever ran a game with no plans made prior?
My Experience:
I ran one game with only one player just to test my improvisation, though i did make a map and a bunch of characters.
Though my only direction to him was i told him where he was and then just asked what he wanted to do.
It ran ok enough but of course was only one person and he was probably better at making goals for his character than others.
I then ran the same game with my group after some refinement but they were alot more lost with what to do which i didnt expect as they had more developed character motivations.
I then ran another game with my 2 brothers with no planning what so ever, I was quite confused most of the time but I think it managed to stay interesting and I probably didnt have to worry about it railroading because there was no plan anyway.
I feel like Improv can be important if your players want to have control over their characters/ the story.
My previous GM i feel was good in that he kept narrative as the focus but it was mostly a game of "can i guess the correct solution (of which there is only one)" which to me felt like a hinderance to roleplaying
All GMs and players have different styles. Some things come with practice and you would GM with different methods depending on the situation.
But i guess for me i like to focus on immersion, i hope to create a strong suspense of disbelief.