The lifetime risk is approximately 1.3% for women and 1.8% for men. For regular smokers: 11.2% for women and 14.8% for men. So about 15 to 30 more likely to get lung cancer. Bringing that down to 4x is close to "almost the same".

No. But that only looks at heavy smokers and duration they stopped, so overselects for old age with higher cancer incidence.

This study looks more broadly, notably also at onset of smoking:

https://jamanetwork.com/journals/jamaoncology/fullarticle/27...

And this is the TL;DR:

“ Thus, those who quit smoking at ages 15 to 34, 35 to 44, 45 to 54, and 55 to 64 years avoided an estimated 100%, 89%, 78%, and 56% of the excess cancer mortality risk associated with continued smoking, respectively”