(Speaking for the US)
Man, 5'9 is so borderline it's tough. I really understand your pain.
5'10 is the widespread social media *magic height* for being above reproach (literally due to just a rounded number, which is ass).
Like 5'8 and below, I'll never question someone for doing CLL.
5'10 and above, your real goal with CLL is to have power / respect / authority.
I'm 5'7 and I'm going to fight like hell to hit 8cm to officially reach 5'10. I know that I'll psychologically be sour if I end up < 5'9.5.
In practice, it's so dumb. Nobody can tell the difference between 5'9.5 and 5'10, or 5'9 and 5'10. It's the stupid social media worms in your head.
I know this isn't an answer, but I just want to let you know I understand where you're coming from, not feeling enough at 5'9, even though it is average height.
What's your race, btw? If you're white, I understand your frustration even more, because average white american is like 5'10 (and we tend to compare ourselves to other members of our own race even more)
I think one thing you really have to think about is sports. If you're really into sports, that's gonna take a hit. I'm a book nerd whose "athletics" consists of casual lifting and casual bjj, neither of which require much standing agility or quickness.
Also: Would internally knowing you're >5'10 solve your issue? Or would you have to hit >5'11 to solve it? Or 6 foot?
If you'd be cool with 5'11 / 5'11.5, 5.5 / 6 cm (2-2.4 inches) on femurs is generally reported to be the golden min-max of lengthening, where you maximize height while taking a minimal toll on athleticism and minimizing risk.
And regarding quad: General consensus is don't plan on it until you complete femurs and give that a test run in society. There's a stat where it's like 80% (or 90%? can't remember) of folks who do a femur lengthening are satisfied and don't go on to a second lengthening.