The best bag I have found, by a mile, is the Peak Design Everyday Sling 5L. It's almost as if it had been purpose built to carry the Mavic Air and accessories. Incredibly well made and one of the best bags I have ever owned (I am also a photographer and have gone through dozens and dozens of bags). I also own the 10L version of that same bag because I liked it so much.
Other than ND filters I don't really have any accessories, but not for lack of trying as I love to buy accessories for my hobbies:
I bought a landing pad, but returned it because hand takeoff/landings are so unbelievably easy with the Air, plus it keeps it perfectly clean at all times and I am super an@l about that.
I bought landing gear and also returned it for the same reason above.
I bought a wind speed meter, but it's use is very limited because A) it's quite obvious if there is too much wind to fly or not and B) Wind can be dramatically different in the air compared to on the ground.
I don't fly anywhere near 4KM away and in most places it is illegal to fly beyond VLOS without a spotter, so range extenders aren't of any use to me. The Air's signal has been absolutely rock solid in my personal experience, even in urban areas.
If you have the Fly More Combo, it includes just about everything you need in my opinion. The case it comes with is also pretty decent for home storage.
If you fly with a tablet, you could look into something like the MavMount which is very good, and possibly a screen shade.
Make sure you get a memory card with a rating of at least "U3" or "V30" (ignore the numerical speed ratings on the card packaging) - you need a minimum sustained write speed of more than 12.5MB/s for 100Mbit footage on the Mavic Air. I don't believe your other drones had this high of a bitrate, so you may not be able to use your old memory cards.
Most importantly, congrats on your new purchase and welcome to the forums!
Just didn't want you to lose any footage! The one you linked is perfect.
