Is there a meaningful difference between monolight and studio strobe, or is this just an example of a couple of product lines overlapping?
The terminology is similar, but not identical. In common usage, strobe most typically means a monolight, just as "flash" most typically means a speedlight. But a strobe or flash is any light that fires a brief burst of ...
Besides the self-contained power supply on a monolight, I would say that it must have a modeling light. A strobe could still be called strobe without one.
Probably the size and power could be expected to be bigger on a monolight, but as there are even speed lights with decent power, probably not.
The SK400II doesn't suport TTL or HSS. In a monolight, you have to upgrade to something like the QT series, or one of the AD battery powered lights.
The trigger supports all the Godox 2.4GHz lights, so it has controls for TTL and HSS. Not all lights support these features though.
There's no difference nor specific meaning in the usage of the terms. These are basically the same thing. Like saying car or automobile, same meaning. However, to me, the term Strobe means a very rapidly flashing continuing light (like seen in some dance halls), which these are NOT. And Flash means a single flash for photography, which these ARE, but some ...