Ok, this is weird.

Trying to install New Roads and Bridges and Let the People Drink

I want to use "LetThePeopleDrink-Cobl.esp" so I don't install "LetThePeopleDrink.esp".

This is the problem: when I activate "NRB4+LtPD.esp" I have a CTD.

This is the solution: I put "LetThePeopleDrink.esp" in the Data folder (but I don't activate it!!) and the game start normally!

Can you explain me why and what I have to do?

Should I activate it or not? Shouldn't I use the Cobl version?

This is because the NRB4+LTPD.esp patch is dependent on LetThePeopleDrink.esp and looking for it.
If you want the COBL version, you should follow the readme instructions;

"Copy one of the .esp files to your Data folder and rename it to 'LetThePeopleDrink.esp'. "

Thank you, now it's finally clear!