When updating foo_openmpt, do you manually do so by fetching a new version from lib.openmpt.org or does foobar2000 fetch and install updates much like other components?
foobar2000 should fetch updates via its built-in update mechanism. I.e. https://www.foobar2000.org/components/view/foo_openmpt (https://www.foobar2000.org/components/view/foo_openmpt) gives you the same thing as https://lib.openmpt.org/libopenmpt/download/ (https://lib.openmpt.org/libopenmpt/download/) does.
Very minor detail:
As foobar2000 still does support Windows XP, the component that is available via the foobar2000 components site and update mechanism is the one built with Windows XP support, as opposed the one built for more modern systems.