After posting the above I spent a few working days aware of the 30 vs 27 debate. I carefully covered the right and bottom edges of the screen with black bars, leaving 27" working area to deal with. My findings are:
- Photoshop and Lightroom work is perfectly doable with the 27" working area
- Doing my other work (my actual paid job) from home is another story: I regularly place two documents next to each other ( | | ) or even a large document and two smaller ones ( | : ) and reach for the resize corners of app windows to spread everything out comfortably. Sometimes I even add a window on the laptop display below.
So historically, coming from dual 17" CRT monitors, a 27" display is already a big step up. But I noticed I got used to the 30" width after almost 20 years. So I am going to stay put for now and see what the market brings. The Apple 2019 Studio Display Pro is 32" which would have been great for me, but the price difference is enormous.
For now, the old lady is still going strong so there is no rush.