I'm concerned that proactive and reactive are on different continua.
Good proactivism has to do with preparation and game design. Detail, texture, and plot are the fruits of this preparation.
Bad proactivism has to do with programing the responses of the players. This is called railroading. The cost of railroading is players' sense of control over their characters and therefore their sense of involvement with the world.
Good reactivism has to do with versimilitude. The world must react to the players' actions in order to seem real. The fruit of good reactivism is a sense of dynamism and excitement.
Bad reactivism has to do with overcompensation. The players cleverly solved one puzzle? Ok, I'll just throw another hoop in their way before they can get their reward. The cost of overcompensation is that players stop caring about being inventive, and will dully hop through hoop after hoop.
So, my world?
Hopefully 100% proactive, 100% reactive. I try to plan maps, npcs, dungeons, plot hooks, adventures, ideas, religions, themes, texture, you name it. I'm human, and probably fall short.
But what I don't plan proactively is the actions of the characters.
Reactively, I have monsters make contingency plans, villages use tactics, NPCs remember the parties, bards tell stories of their deeds or crimes, the world spreads and changes in response to the party's actions.
But what I don't do reactively is take away the rewards of cleverness from the party.
best,
Carpe