Does the method mentioned for the Qiyam al-Layl prayer—which is to pray eight rak'ahs consecutively, then perform tashahhud in the eighth, then stand for a ninth and perform tashahhud in it and then say the taslim—suffice for shaf’ and witr, or do shaf’ and witr come after it? And is this method the best of what was narrated from the Prophet (peace be upon him) regarding his qiyam?

The characteristic mentioned in the question, namely performing Witr prayer with nine continuous rak'ahs, is among the established characteristics reported from the Prophet, peace and blessings be upon him. The evidence for this is what 'Aishah, may Allah be pleased with her, narrated in Sahih Muslim, that the Prophet, peace and blessings be upon him, used to pray nine rak'ahs, not sitting except in the eighth rak'ah, where he would recite the tashahhud but not give the salutation. Then he would stand and pray the ninth rak'ah, recite the tashahhud, and give the salutation. The best way to perform Witr is for the worshipper to give the salutation after every two rak'ahs, then conclude with a single one.