As far as i know it scales differently if i remembr correctly. One arm chin up is easier then 2h chinup with weight belt equal to your bodyweight. Having sayd that it doesnr mean that you can do 1h chin up if you can do a 2h chinup with bodyweight hanging on a belt, you have to train for it specificly.

And you have to be light. Its significantly easier to do if you weigh less. 60-75 kg bodyweight is ideal imo and makes it alot easier

I recomend book ross enamait never gymless. There is guide how to achieve it and ross sells the book on his page for 1$. Ross is katie taylors coach and a legend he knows his shit good every page in his books is worth its weight in gold imho