I have seen videos from the company showing them flying with the clear plastic cover on the drone, but some YouTubers say fly without it. I think it catches unwanted flare/reflections and may interfere with the cooling fan air flow. Thoughts? Does it help the gimbal hold steady if the cover is affixed?

Fly with it off. Glare and possible over heating.

Agree, off definitely gives a better quality image

Hi sir, it is always the users' preference to fly the drone with or without the gimbal cover. It will protect the camera from the wind to some extent but might also sacrifice the resolution or quality of the pictures and videos in some situations. So you can fly with or without it according to your needs.

I call it the bug shield.

Fly with it off.  They make hoods if you want to go that route.

^^^ yeah don't use the gimbal clear cover and although I bought the hood, rarely used it. For me it seems to get in the way. Good for some shots to block the sun but rather use the ND filters.