I'm running a 370cfm w/ dual intakes and its barely enough for me smoking solo. I have it on a timer based on @WNYTONY setup and it'll continue to clear the room after I leave. The Rabbit Air does wonders for clearing any odors.
I am in the process of finishing my room which is a 20’ x 17’ with 9’ ceilings. now to be fair my room is not in my livable house but my 40x60 metal workshop. I originally thought that the two Rabbit Airs I purchased would be enough but added the large Renpho which has helped. I am still planning on adding a ERV which will cycle the air in the room and exchange it with fresh outside air on a set schedule throughout the day. This is a must because of how tight I made my room in an effort to keep in the smoke. Once that is done, I can better comment. Here are a few pics so far.