On the download page of the "Black" Series III mixers you can find the "StudioLive Series III S Comparison Guide", which will answer your questions. Follow this link: https://www.presonus.com/products/StudioLive-32SX/downloads
The SL 32SX is missing Blue Tooth, the Fat Channel and DAW scribble strips and the dynamic Fat Channel Controls. Otherwise the mixers are technically the same. You will not get the free Fat Channel Plugin Collection when you purchase a SL 24.