i7-9700K offers about 10% better performance than the 2700X for this[0][1] for about the same percentage increase in price. Pretty decent. Worth noting that the i9-9900K and i7-9700K are about the same here.
I dunno where you are getting your numbers from but currently 9700k is approximately 40% costlier than 2700x. $420 vs $280. Heck - I can walk into nearby microcenter can get both 2700x CPU + motherboard at $350.
10% doesn't matter if it exceeds what your monitor can handle. For example, in Tech Report's benchmarking, even a i5-8400 is well over 60Hz in many current games at 1080p on maximum settings. [0]
If you want to run the latest games on max settings at 4K/120hz, it's a different story. Personally? I remember when reviews gushed over 30fps at 800x600.
No one much cares about the framerate in civ6. It's about AI turn calculations in the end of the game, which is what the benchmarks people were linking are.
But it's turn based— most of the time that you're playing, nothing is happening! Surely it could be running its simulations and AI speculatively and then just tossing out the bits which aren't relevant any more as the player makes changes to the world state.
The number of possible things you can do is a Large Number, so I doubt how possible this would be. Even if it were - it would absolutely murder battery life. Civilization runs on laptops, and now iOS too.
Most turn-based bots are in some way derived from minimax— you peer down the road looking at the space of possible moves and evaluate them based on an assumption that your opponent will respond with the strongest possible move available to them, so each move you can make now is only as good as the game state after the opponent's response, recursively.
I think basically as you're building up this tree you'd add annotations at each branch/ply which call out things the human user (opponent) could do that strengthen or weaken the position. Then as the human performs their actions, the tree is pruned/rebuilt accordingly.
Yes with Chess you can do exactly that no problem, but I bet Civ has a thousand heuristics woven through that which would make it horribly difficult. Maybe not impossible though!
The other complication is it isn't just 1 on 1, its 1 player vs ~10 players. So your move changes player 2's move changes player 3's move and so on.
