No, the perks don't cap out at 50. I just read online about someone who said they reached 51 and got a perk for it. The perks that I have found the most useful are in the one-handed category. You can eventually double their efficiency, and you can also make it so maces ignore up to 75% of armor. Other than that, my perks would not work for a their/assassin. My character is more of a paladin type where I'm a tough warrior that relies on restoration and enchanting.
Even if the open windows of science at first make us shiver after the cozy indoor warmth of traditional humanizing myths, in the end the fresh air brings vigor, and the great spaces have a splendor of their own - Bertrand Russell