Your questions about SoFi Hong Kong are answered here

Safe: eDDA complies with the regulations of both the Hong Kong SFC and the HKMA.

Optimized: You can initiate an instant deposit instruction in the app without the hassle of uploading the transfer proof.

Free: eDDA setup and the deposit service in SoFi App are free of charge.

Instant: After initiating the deposit, funds will normally arrive within 5 minutes.