Solid core, 22-24. For the most part.
Pre-bond is too brittle for my tastes...stranded...well, the really finely stranded stuff is a PITA. A stray whisker, blah.
But...if each strand is thick enough, it certainly makes it a lot easier to work with.
I I'm not keen on PVC insulation. Too easy to melt. PTFE and Silicone are much more resilient...a stray touch with a soldering iron won't do a thing. Which helps with maintaining sanity.