Hi, I have a simple question. I have the DJI o3 system and im thinking how to record best footage on my 5inch. I have a gopro hero 6 and dont know if I should invest into ND filters for the GoPro or the dji o3. I might also want to buy the dji action 2 but I’m not sure. Can someone give me some advice on what I should do?

It will come down to your preference and in what kind of lighting you fly. If you use the O3 as your main recording camera, then your FPV camera becomes restricted to the recording settings you select which may make it difficult to fly (for example if you are sensitive to latency, you will struggle with 30fps and even 60fps maybe noitcable - or if the camera is exposing for the sky, the ground will be very dark and hard to fly; also if you fly in 16:9 then you can't record  in 4:3). Whereas with the gopro you have the flexibility to adjust the framerate/exposure best for the lighting conditions or output you want, and set the FPV camera for best flyability. If you do a lot of recording in lower light, then I think you will have to use the Gopro.

In terms of image quality, I believe you get higher bitrate from O3 and it does 4k up to 120fps (if you want to slow down in post) whereas Hero 6 you are limited to 4k 30 in 4:3 mode. Some people like gopro color balance better, DJI will tend to be a little colder/more contrasty. You can record with both and decide what you like. Hero 6 still gives some real nice video, but side-by-side O3 probably captures more details.

As for Action 2, I found the image quality very similar to the O3.

Here is a clip recorded on the Hero 6
https://youtu.be/FHWOtBGjpCI?t=1

And one on the Action 2, not the same lighting but hopefully you can still get an idea
https://youtu.be/up43td0wBsw?t=199

Hero6 is old sensor technology and a step down from the 03 in regards to resolution and dynamic range. As far as color it all comes down to how skilled you are at manually setting white balance in whatever editing software you use as well as how you color grade. It's an art. ND filters have their place but are overused and improperly used many times. Motion blur is cool only if you are not panning or tilting too fast. The faster the action the worse motion blur looks. In the cinema production world there are unwritten rules about how fast a camera should pan relative to the shutter speed. It's an art.