I have done some more testing with GCam5.1.014-Arnova8G2-v9.1 and MGC_5.1.014_7.0H_C2API_v.1.3_AllinOne (Settings Pixel (corr); Nexus 6 (max paramaters = High); Default.). I was mainly focusing on maximum image quality and not default processing.
* Auto post processing on ported APKs is bad in tested conditions (forests). Especially blacks are often crushed. White balanced is a hit or miss. Overall sometimes it looks almost natural, sometimes as an artistic interpretation.
* DNG from ported APKs retain all detail of HDR+
* DNG from ported APKs are better than normal DNGs (used Camera FV-5). Main difference is noise, which is more under control. Dynamic range is better, but it's hard to test. Noise from Dark Current is reduced.
* GCam5.1.014-Arnova8G2-v9.1 seems more stable for taking DNGs
link to the all apks
https://www.celsoazevedo.com/files/android/google-camera/