How do you avoid as much as possible bikesheding about style guide (even passing to standard), spec style, only service object, premature optim ?

Every few months when you think that it's over. You have new colleagues, and you have to start from scratch. It consumes lots of energy especially with strong opinions.
+ it happens less I want to be involved, but I know that one day I will be annoyed by those choices (painful refactoring, project hard to test, hard to understand, unmaintained tools)