This kind of “workflow” was always my biggest issue with the Nik Collection. Used as plugins it is somewhat ok-ish. But it is not non-destructive in the sense that I could change or eliminate an intermediate step later. Even repeating the same step for multiple pictures is more difficult than it should be.
About the Photos question: 90% of the time Photos (on MacOS) is the endpoint of my workflow. I do not bother with importing/exporting then importing again. Also I found Photos sometimes behaves weirdly when I import the edited picture: it vanishes from the library again apparently because it has the same metadata. In this case i use Exiftool to add one second to the date and time fields so that Photos doesn’t recognize it as a duplicate. To annoying for my regular workflow.
If I start and even edit in Photos then it was an unimportant picture from a mobile phone in the first place. Recently I edited some DSLR pictures while traveling with Photos on iOS and Snapseed so I could share them the same evening. After coming home I re-edited all of them with PL and got much nicer results.