After bowing down, (ruku), you say: “Sami’a Allaahu liman hamidah (Allaah listens to the one who praises Him).” This is obligatory.
Whilst standing after ruku, he should say, “Rabbanaa wa laka al-hamd (our Lord, to You be all praise).” (There are other kinds of dhikr which may be said at this point.). This is obligatory for every person who is praying, even if he is following an imaam, because this is the dhikr of standing after rukoo’, and saying “Sami’a Allaahu liman hamidah” is the dhikr of straightening up from rukoo’. It is not prescribed to put the hands one over the other during this standing, because this was not narrated (from the Prophet (peace and blessings of Allaah be upon him)).
There are differences in opinion because of the various interpretations of the Qur'an and Sunnah. My advice would be not to worry too much about these various sects and stick to the sunnah. Perhaps the Prophet did a certain action in different ways - one way isn't worse than the other and you're following the sunnah either way.
See
https://islamqa.info/en/13340 for a description of the Prophet's prayer.