Just so we're all on the same page:
Xwave was just the retail sound card branding used by Labway.
https://web.archive.org/web/20010309111516/ht … m/xwavepage.htm
I believe Labway cards can generally be identified by the "LWHA", though the fancier looking "Waveforce 192XG" doesn't seem to have this numbering, it should be functionally the same as any other YMF724 PCI card (though there are lots of cheap knock off cards that aren't made properly). I don't think Yamaha built the card because any examples I can find online say "Made In Indonesia", but they certainly took over the branding of it. It had it's own website!
The YMF718\719 and 724\744 are very different, so I wouldn't say that one is a PCI variant or an ISA variant of the same type of device. They both use Yamaha chips and have built in OPL3, but they're from a totally different generation, with the PCI based 724\744 being more focused on Windows support with hardware assisted GM\XG wavetable synth available under Windows (in a DOS box, but not in pure DOS). The 71x series are focused on DOS support and have no hardware wavetable assist at all, and instead rely on the CPU to run a software synth like S-YXG50 under Windows. S-YXG50 can be run on almost any sound card though, as far as I know.
Here's a great writeup of the features of the various YMF 724\744 based cards out there.
Yamaha YMF7x4 Guide
The Xwave brand was also put on non-Yamaha based cards like this ESS Allegro "Xwave 512":
http://telecommander.com/pics/links/Sound%20C … /essallegro.htm
Now for some blitting from the back buffer.