The job of USCIS 1) to see if there is anything that can disqualify a petition, and 2) to verify the information provided, and by extension, the validity of the petition.
One thing going for you is that you do not need to establish proof of bona fide relationship for the I-129F. You just need to provide proof of the 3 basic requirements: the petitioner is a US citizen, both parties are free to marry and intend to marry, and the parties have physically met within the last 2 years. USCIS will also check that the petitioner does not have a criminal history that bars from qualifying. The approval of the fiance visa itself by the embassy is a separate matter, which requires background checks of the beneficiary, relationship evidence, and other requirements.