Well, Cerebus, pretty much all of the good editing software programs, whether by Premier Pro, Avid, Final Cut, whatever you use, have controls for brightness, contrast, some for saturation, or color vibrance, so you can add or subtract type and depth of color to taste.
The ND filter just allows for a slower shutter speed, given a constant lens aperture and a very bright sun, by cutting down on the amount of light that enters the camera, like sunglasses. It's the same as closing the aperture down a lot, but if you actually close the aperture down past, say, f/5.6 ot f/8 on some digital cameras, the sharpness of the image actually gets less due to lens diffraction and other digital issues. So most folk add an ND to keep the lens aperture in its sweet spot, around f/5.6 or so usually, and the shutter speed between 1/50 and 1/500 of a second. There are different strengths or grades of ND filter available to allow for this control.
The Polarizing filter is another kind of filter. Light reflecting off water, glass, whatever, has a partial polarization to it. If you use another polarizer, e.g. the filter, you can control the amount of light reflecting off the surface. The most obvious example of this is being able to see the people inside a car, for instance, shooting through the windshield. With polarizer, see inside. Without polarizer, see only the reflection of the sky, clouds, in the windshield, but not the people inside.
Is there a combination? Yes, there is. ND polarizers are more expensive, but not impossible to find.
The different brands and types mainly allow for (or obstruct) the motion of the camera and gimbal. Some you can keep on all the time, but others will block the gimbal from rotating freely, or even initializing properly, and so you have to start, self-calibrate, etc the camera, and then put the filter on it after.
I had a problem on a Phantom 3 where the filter and lens hood were too heavy for the gimbal motor to hold up comfortably. I could hear the motor whining as it struggled to hold up the weight. I ended up not using the hood, just the filter. The whine went away immediately.
So all that color enhancement stuff is easily learned via regular photo how-to websites, and off photo sites like 500px.com, that offer many tutorials, suggestions, and most importantly, sample looks and how they were gotten to quickly and easily.
For video, there are several pre-programmed looks packs available, notably Magic Bullet Looks Suite for the editing programs mentioned above, that let you select an overall look that you like, and then fine tune your own and save that out as your own custom color preset. Movie film looks are catered to by folks like filmconvert.com, that have the proper camera profiles for all DJI products as well as every other camera, to give it whatever movie/film analog look you want, and tweak that too.
Any cool photo has a series of filters and tweaks that will 99% of the time also apply to video. Similar controls and settings exist for both, or else it's not too hard to find equivalents of or analogies to, say a Photoshop filter, but used in Premiere Pro, for instance. A lot of plug-in companies will make the same color preset programs for both stills and video, with the same controls, so feel free to reach into the stills world, get the look you want and an idea of how it was done, and then apply that to your own videos!
HTH
Best
Chris