It seems the general consensus is not to do D-Log but Art for doing your own color grading. The difference is pretty apparent. On the Mavic, D-Log doesnt have the depth available. And the latest firmware has degraded it even more. Art is allowing better results.
I shot this with a friend of mine - he wanted to get his hands on a Mavic and test out the different modes. He ended up liking Art at -1,0,0, and it looks like I will be moving over to that as well. I am also going to be shooting in 2.7k rather than 4k. Youtube just doesn't stream out 4k well enough. And then, while the 4k monitors are on the rise, the average user isn't streaming in 4k anyway because their connections wont support it. There are other reasons (data stream from the chip is only 60mbps which is barely the minimum for 4k) as well. Besides,
As to what to use, it is going to be hard to beat DaVinci Resolve for its price. iMovie, if I remember, doesn't support 4K (it has been a while since I even opened it, so could easily be misinformed) so there is no real point in it.