Broadly speaking, it's fully backwards compatible with the Sound Blaster 2.0 (and by extension the original Sound Blaster). This then also makes it compatible with the Adlib sound card, since the Adlib also utilised the very same Yamaha OPL2 FM synthesis chip. However, take note that the Sound Blaster Pro 2 and later Sound Blaster models does utilise the Yamaha OPL3 FM synthesis chip (the YMF262), whereas the original Sound Blaster utilised the Yamaha OPL2 FM synthesis chip (the YM3812). From a gaming perspective, it makes no real difference, apart from the fact that the OPL3 is a stereo synthesis chip and has more channels, whereas the OPL2 is a mono synthesis chip. Therefore, later games that were written to make use of the OPL3 FM synthesis chip's stereo capabiltiies, will sound better on a Sound Blaster Pro 2 or later sound card.
The CT1600 is referred to as the Sound Blaster Pro 2, since you had an earlier revision (the Sound Blaster Pro 1) that utilised two OPL2 FM synthesis chips in order to produce stereo sound output. Some games, that were specifically written to make use of this, will not sound correct on the Sound Blaster Pro 2.
No Sound Blaster card was ever Windows Sound System compatible (unlike many clone manufacturers) since you require a specific CODEC chip (the most popular ones being the Analog Devices AD1845 and the Crystal Semiconductor CS4231A codecs, and their later variants). There was no reason for Creative Labs to have extended support beyond their own standard (since Sound Blaster was the de facto standard).