TFSA is generally not a trust, which means F.3520/F.3520-A should normally not be applicable.

The tax-free savings mechanism is, however, not recognized for US tax purposes.  This means any earnings arising from the account should be reported as taxable income on a current basis.

Since TFSA may be invested in vehicles such as mutual funds or similar securities, your client could be subject to PFIC reporting and its punitive tax regimes although certain elections are available to mitigate the tax impact.  You will need to review the types of investments your client has in the account to make those determinations.

Because TSFA is a foreign bank and financial account, it will be reportable for FBAR.  Similarly, assets held in the account are subject to FATCA reporting.

Not sure why your think F.8858 is relevant though.  You mentioned there are conflicting opinions.  Could you elaborate?