I used to use SFZ and probably still have it on the DAW somewhere.
The whole sound font thing was a bit confusing to me, even after having done it....(adding some new ones) several different times. Some of the confusion came from the fact that not all the sound fonts actually worked properly. More than one time, I downloaded a font, unzipped it and installed it and it refused to work. So it was for me a hit and miss issue. Most did work and sounded OK.
There were, at the time, at least 2 different formats and they both used different unpackers to install the fonts correctly.
I had quite a collection of fonts on my lappy at one time. However, when I built my DAW I decided to switch to all sampled sounds and left the font based synths behind. To my ears, the samples generally just sounded better.... more realistic, than the fonts.
HOWEVER... the main reason for popping in on this was to tell you that on my website, click on LINKS and the 4th and 5th links down are to websites with FREE sound fonts and I just checked and they are still active sites. I managed to pick up some nice ones there.