Ok, it turns out I didn’t scroll down enough to see the dn x hd 444 option :]
I was reading this article:
https://www.eoshd.com/content/12140/discovery-4k-8bit-420-panasonic-gh4-converts-1080p-10bit-444
Apparently converting 4:2:0 4k files into 4:4:4 1080p could benefit the footage because of all the extra pixel information in 4k.
“The way this works is quite technical but it essentially amounts to using the extra pixels present in the 4K files to rebuild the lost colour information. Neighbouring pixels are summed to create a super pixel with a greater bit depth and better sampling. It requires a lot of processing power and a finishing codec good enough to store the extra colour data (10bit 4:4:4, with CineForm and ProRes being suitable choices) which is why the camera doesn’t do it internally. It does require a transcoding step in post but the increase in quality over the 8bit internal 1080p codec will be marked. The message is clear. Even if you’re working in 1080p, shoot 4K on the GH4 if you want the best quality.”
Though I don’t know enough about codecs and the science behind all of it to really make a judgement. Thought I’d try it out.