Thank you so much! I am leaning towards the GoPro Karma because I can set these paths and just put the controller in my pocket. I really like cable cam.
I've read that the Mavic's follow feature still has some flaws. With the Karma, I can "fake" follow by using the cable cam to produce something similar. If I bike around 10mph, cable cam could produce some pretty cool photos.
Sadly, this is not the case. Here is why:
Cable Cam is not a fake follow me because it follows nothing and the camera is stationary. Let's say you pick two points about 100 meters apart. Karma will fly between those points at the speed you set on the controller. This means if you're on a bike, the bike path must then be 100% straight between the two points. Next problem is where is the camera pointing? The reason drones have Cable Cam is so that the operator doesn't have to fly the drone in a straight or curved line while also pointing the camera at a stationary or moving object. It would be next to impossible to ensure you are in the framed shot.
Maybe the Karma, version II (hopefully out at this time next year) will have the ability to do what you are asking.
As for the Mavic. Have a look at the Phantom 4 tracking that was out earlier this year. It has been further refined in the Mavic Pro. Tracking in the Mavic Pro now lets the camera follow you from behind, from in front or from the side. It will track anything larger than a pineapple as long as the object does not blend in with the surroundings. From experience with the Phantom 4 and now the Mavic, it works extremely well. But don't take my word, just watch the hundreds of videos of people doing exactly what you hope to do with the Karma.
I'm not pushing the Mavic, the decision is yours, but you may want to consider making a list of what you'd like your drone to do for your needs alone and see which drone works.
As I mentioned before, if you want a drone with a removable camera, then Karma is it. If you want the fisheye camera image along with linear image you can get with the Hero 4/5, then the Karma is it. If you want a drone that is super simple to fly because it has very few features than the Karma is it. If you want a drone that comes with the display screen built into the controller, then the Karma is it. If you don't mind carrying plenty of weight on your back, then the Karma is it (I don't have the Karma yet but everyone who has weighed it says it is the heaviest drone out there (amongst 6) in its price range).
I'm hopeful that GoPro, within the next 6 months, will add a feature to the Karma controller so that the Karma drone will follow the controller so that it can sort of do what you would like it to do. You would not be able to stick the controller in your pocket, you'd still have to keep it flipped open for it to function. Unfortunately right now that does not exist.
This may help give you an idea of what Active Track is on the Mavic: