Owner of the Action 2 here for 7 months, recently in August I did its first serious test in adverse but reasonable vacation conditions.
So far, my opinion is that the camera is excellent for many reasons that I will mention below.
Firstly, if you want an action camera for extreme sports such as surfing, skydiving, skiing, but even for timelapse on a motorcycle, then I recommend the GoPro for you or the Action 1.
Beyond that, for anything else, I recommend the DJI without hesitation.
It is the ultimate incognito travel kit to comfortably capture all your moments on a trip, without difficulty in transportation, always in your pocket. Not that it can't do extreme sports, it's just definitely more fragile than a GoPro and it wasn't originally designed for that use (they had vlogging more in mind).
Positive elements after vacation:
-The most useful mounts, apart from the tripod head, are definitely the necklace, mainly for transporting the DJI, so you can always have it around your neck wherever you go and ready for shooting. The magnet is very strong and doesn't come off in normal conditions. Especially on vacations where you often may not have pockets or are holding things, it's the best thing, you have it around your neck and whenever you see something, boom, you capture it.
-Amazing battery, it never runs out in a whole day, and simply every time you're not using the camera mount (or the battery mount you have), you attach it to the bottom body and put it in your pocket, and it's back to 100% until you take it out again.
-Now, the overheating issue that received a lot of hate on its release, under normal conditions you will never have a problem (it has never overheated for me, by the way). Now, if you set it to record video at 60 and 120 FPS below 40 degrees Celsius under the Greek sun, even you would overheat. In any other conditions, especially in a situation underwater (where the camera is completely waterproof), it has absolutely no problem. Something extra is that sand doesn't stick to it at the beach due to its construction material. (It's good to have only the camera out at the beach and attach it to the battery module when you return home or after rinsing it in a tap).
-My way of using it was to have a memory card (64GB) in the battery mount, so as soon as I returned from the beach or a walk, I automatically transferred all my files from the camera to the SIM card. So on the next outing, I had 22 free GB to use until the evening. Generally, it had enough space. For 10 days of vacation on 2 islands, it was more than enough. (The clips I shoot don't exceed 1-2 minutes, and most are 10 seconds). If someone needs more, they can simply get a larger SIM card.
-Low light. The low light performance of the DJI is very good compared to other action cameras, and even the stabilization is good without producing strange artifacts, but remember to set it to 60fps, otherwise the shakiness is noticeable at 24 and 30fps. From the moment you lock the exposure at a maximum of 1600 ISO, it won't produce much noise.
-Now, for the sound, the DJI has a very strong point, especially if you have the 3 microphones. Specifically, for the parts where I want to speak clearly to the camera, I have attached a Saramonic USB mic that works very well with the Action 2. The microphones themselves do a good job, and you need the 3 of them more for sound direction than for extra quality.
The other solution I found and is an excellent choice was to get a Samsung USB-C male to 3.5mm female adapter and attach a luv mic to the DJI. Excellent sound performance.