@peemee I used CCC in the noughties but had a disaster with it (might have been human error). After that I used SuperDuper! happily for years but had some issues recently and considered ChronoSync because I'd always heard good things about it. I've been using that for a year or two and it's been great. Recently though, it was telling me a volume had 1.5TB of stuff on it when it only had 600MB, meaning it refused to back it up to a 1TB drive.
Today, after your comment I installed the CCC trial and it looks like it's filled-out over the years. First impression of the interface was so-so. Second impression was good because the way it reads and displays A.P.F.S. volumes and volume groups is good and the most accurate. And it's not making that mistake ChronoSync was making so it allowed me to do that backup I wanted. I've not got the legacy bootable bit working yet (it tried but gave errors). Will try again though…