You are confusing "change o status" and "visa application".

Change of status is processed by the USCIS, whereas visa is received in a U.S. Consulate abroad. Either process should take less than 6 months, as you suggested. It really depends on the Service Center and the local U.S. Consulate.

RFE is always a possibility. An accurate preparation of the application should minimize such a possibility.

You should consult with an immigration attorney prior to filing your papers.

Best regards,