I have never used a still air, but what I've read is that with the fan you can keep the set temp a bit lower since theoretically all the air in the box is the same temperature, where with a still air the air at the top is warmer than the air at the egg level. Most people say never put the plugs in, for me that doesn't work because it is so arid here, so I leave them in, but I have yet to have a great hatch, so you might not want to go by me LOL. It's tough to hatch at this elevation (5400+) and aridity, but usually if my own birds lay eggs that are fertile I do okay. Still have failures but not nearly as bad as with shipped eggs. Anyway, for just about everyone else I'd say leave the plugs out to improve air flow.
I would use stout paper just in case there's any condensation when setting eggs. Sounds like you will have an interesting hatch!