Visa for conference in Kunming

I plan to travel to an academic conference in Kunming in September. I have a letter of invitation from a professor at a Chinese University. Should I be applying for an "L" or "F"? Also, my passport will expire in January. Do I understand correctly that this is okay as long as I apply before July, even though my trip is within 6 months of the expiry date of the passport?

Thanks, Joy.