Points are based on achievement rarity, if a game has lots of players but only a few manage to get all the achievements, the points for that game should be high. The hours of playtime doesn't affect or count for the leaderboard, on some platforms, people can also play and earn achievements while in offline mode.
I think, the profile refreshed a couple times in a day, and how fast the achievements being tracked here may vary depending on the platforms, but you can do manual scan.
At least that's what I know, I might be not 100% correct.
What WISiGAMI said is what I understood as well. There is the official announcement of the EXP system, but that goes back to 2019 and I believe the algorithm has received some fine tuning updates since then.