My humble suggestion to the new joinees of the forum is to take out time and browse through the older posts. Many of your questions would have been already answered in older posts.
Use the "Advance Serach" option on top right hand side of the webpage to search older posts. Input simple keywords in the serach box. For example in this case input text "rehras sahib" in the serach box and you will find older posts.
The reason for this suggestion is that, the same question would have been already answered 3 - 4 times on different occasions. So the existing members may not feel like jotting down the same answers again and again. Eventually, the new joinee of the forum feels let down that nobody is answering their queries.
Coming back to original question.
Short answer to the query is that, atleast do the nitnem, of 7 banis, of the version which is being recited at Sri Darbar Sahib, Amritsar. That version is accepted as per the Sikh Rehat Maryada issued by Sri Akal Takht Sahib. Once you start getting "Rass" and feels like reciting more "Bani" then there is no harm in that.
The Audio files and Gutka Sahib which you refer may have different versions becuase every jatha has its own traditions. Tarna Dal, Buddha Dal, DDT and other sampradas have their own versions of Gutka Sahib and the length of Banis will differ.
Don't fall prey to controversies of long or short or sampooran rehras sahib etc... Every Shabad of Guru Sahib is sampooran in itself. Take a head start by following what is being recited at Sri Darbar Sahib, Amritsar.
Bhul Chuk Maaf.
Waheguru Ji Ka Khalsa,
Waheguru Ji Ki Fateh.
ਸਤਿਗੁਰਬਚਨਕਮਾਵਣੇਸਚਾਏਹੁਵੀਚਾਰੁ॥