Thanks John
I always process as a 16bit TIFF, then downsize using the Alex Nail plugin to the 'instagram' option (1080px longest), adjust the sharpening layers to taste, flatten and save under a new name, which is basically the filename addended with the longest side px dimension (aka _1080). In CS6 I then 'Save for Web', though I see that is available only as a so-called 'legacy' action in CC, so I assume has been rendered unneccessary. The Nail process converts the 16bit TIFF to an 8 bit jpeg automatically. It is/was a useful shortcut.
What resolution would you suggest setting for my 1080px longest?
Interesting. Nail hasn't produced an update since 2017, and has removed all the downloadable files from his website. I've got v5, but when I unpacked it earlier it prevented CC from opening until I had rebooted my PC. However, having done so, it still wasn't available in PS CC. It’s a useful timesaver, and I'd love to find a way to get it back.