Recommend me a good system for a game of intrigue

So, I'm looking for something more specific than just intrigue:

• I don't care about setting.
• We're 4 people in total.
• I want a improv heavy game. The kind of game that asks the players to build the setting with the GM. It could also be a GMless game.
• A game that actively encourages or directs the intrigue with its mechanics. I don't want a "you 'COULD' run something like that with X game...", I want a game that is actually about intrigue.

Also, I there's a couple of games in this style that I already know of and would appreciate your opinions on:

• Urban Shadows 2e. I played a 2 or 3 session with my group. I found the faction play really clumsy, but maybe that's just me.
• Kingdom. We played a one shot and had some fun. Are you supposed to use your scene to freely introduce narrative context to the question in play? (ie: Question: Should we preemptively attack the outsiders trespassing in our forest? Scene: I send one of our scouts to learn more about this strange group). That's how we played it, but I'm not completely sure if that's what's intended.
• Swords of the Serpentine. I would love to do some swords & sorcery, and really liked the setting, the little that I read. But I've never played a GUMSHOE game, so I'm not sure how much prep it asks for a mystery, and how far you can go with purely improv. After years of playing purely mystery games, I'm pretty tired of preparing for them.

Thanks for your time and I'm eager to see your opinions and recommendations!