Leaderboard

Yes for 4K the bitrate are very similar (I am around 780Mbps for ProRes HQ in 4KDCI) But for 6,2K I have a bitrate of around 2300 Mbps with ProRes HQ. This is really different from the 720 Mbps of H265 (Angelbirds SE 512GB cards are very good at a reasonable price, I got some around 180 euros) https://www.angelbird.com/prod/av-pro-cfexpress-se-type-b-2919/?category=238

I don't think the issue is Phase Detect because V-Log on the S5II (while sharper than before) has not the insane sharpening and chroma noise reduction that the standard profiles have. Moreover, nor my A7III and IV smooth details like this at low ISO and yet they use Phase detect. There are just bad processing going on internaly on the standard profiles with the S5II.

I needed similar in-camera and external resolutions for a fair comparison. 6.2K was the only way because in ProRes RAW you only have full-sensor 6.2K or cropped 4.8K. I don't have a CF card so I can only record ProRes HQ to the Ninja, and 6.2K is not available there, it's only available in ProRes RAW mode. This is the reason for internal H.265 instead of ProRes HQ. And if you record in UHD 24p, internal H.265 has actually more bitrate than ProRes HQ (720Mbps vs 707Mbps). I tested it, H.265 actually looks better due to more efficient compression. To you other question, I did not use any LUTs during my testing, I usually work with color space transform or aces nodes.

Just out of interest, why do you need to shoot 8K on a phone?

Summary of my findings so far:

Yes, softer image = more filmic somehow.