About a week after completing the move to the W3C template, I happened across Bootstrap Studio, and it looked rather funky. So I bought it... And then remembered how much I hated Bootstrap in the Joomla incarnation... But I started looking at converting the site to Bootstrap 4: far from a painless process, and a weird learning curve that rose very little but then more steeply once the concepts had started to seep through. Needed a lot of online help though, struggled to get the barebones of the front page created, and disappointed by the lack of control over the HTML it generates. All very hard work and not sure I want to give the time to changing the whole site.
And then yesterday I came across CSS Grids, and what a revelation! Such a simple and powerful methodology, so I'm trying to gen up on that now. Once I find out how to do a fixed menu bar with dropdowns, another conversion may well be on...
Best to keep things simple, of course. I can continue using W3C for the menu bar, leave current pages as is (except for pic pages, which look better with CSS Grid), and use CSS Grid for future changes and new pages.