Because Twig files might have a lot of nesting, it can be useful to define a separate print width for Twig files. This can be done with this option. If it is not set, the standard printWidth option is used.
However, since a default value is given for twigPrintWidth, it will never use the default printWidth. One has to override both options to have the same value throughout different files in a codebase.
The README says:
However, since a default value is given for twigPrintWidth, it will never use the default printWidth. One has to override both options to have the same value throughout different files in a codebase.