Some further comments after playing with it more:
-> An 'Old Forum Comparison' I was playing with included having the inverted CSS colors turned on (and I may make a pic for archival/wiki use, using a 'public' thread). That does make it look a lot like the new forum's dark color set, more than I thought at first.
-> I'm actually getting happier about the layout; the dividers aren't nearly as bad as their first impression, particularly when fiddling in Portrait mode on the Surface tablet. Its also faster to read and compose on large screens like the one I'm on now, and because of that also reduces eye and neck strain in the long term. This is the same reason why I learned to live with what Wordpress was doing to my site.
-> I found it interesting that the common denominator for the standard width appears to be a 13" notebook in landscape mode. Even my Surface Go (which would be considered 10" in the normal laptop config) was too small, and actually generated more lines in a paragraph. But at the same time, it was far easier to browse the site in portrait mode than the old one (just generally browse, not take any advanced actions like others have done).
-> Decided not to generate a set of shared pics, since its transient anyway, and I also felt that the differences (between the various screens, not between the forum views themselves) didn't warrant that level of comparison after all. If Ian specifically needs feedback on views like the Surface Go, he's welcome to ask, for which I'll PM him a link.
-> It should be noted that the removal of Location, Join Date etc on posts may eventually be required by laws like GDPR (depending on later interpretations), and later privacy/PII laws coming down the pipe; given the international readership, I certainly can't fault Ian for trying to future-proof any headaches down the line there. So long as the User Profile (requiring an account login) still has all these details, I don't see a problem with it. The removal of User Title is obviously less so, other than helping to compact the view; I can personally live with that by moving it to Profile and/or Sig.