Yeah, this covers it partially but nothing close to dt in this regard yet. TBH I didn’t play with it much because vkdt discards all the changes for me every time.
Not practically acceptable in the long run, first of all because it may be easily overwritten by the next update and all the struggling will be lost. Then, I leave manual fiddling with the config files as the last resort. More or less frequent things ought to be available via UI somehow. Also please consider copying all these files under ~/.config and use only from there. It will give another level of protection if editing goes wrong. The originals should stay untouched AFAICT.
Practically presets did not look very obvious to me ATM, either. Probably I shall spend some more time with vkdt. I think, because vkdt, in a way, may be considered as a dt successor to some extent, it would be nice to have the UI as close as possible, to make learning curve not so steep. I don’t suggest to make an exact copy, not at all, but leave some continuation wherever it’s deemed reasonable instead. Otherwise users will be unduly confused, which in turn will have a negative impact on a user base. Because I think you’ve left the proof-of-concept stage behind, it’s a high time to give the usability matters some more love. If I can’t do whatever I want to the image after some reasonable amount of learning because I can’t manage to master the UI, then no matter how fast, reliable and generally good the processing itself is. So far I’m rather struggling with vkdt’s UI than really testing its processing capabilities. But even this way I’m impressed!
I wouldn’t call standalone Compiz bloaty in any way 
Anyway, the command/hotkey for exiting is a must IMHO.
re: 4. Please consider fixing it, and I’ll test.
I am AFAICT. vkdt shows some exif data (camera/aperture/iso…) but that seems to be it. No orientation, no black points or whatever. WB maybe…