SFZ+ was a ray of sunshine when it first came out, but bugs and ironic limitation plagued it. Half baked and stuck in time.
It could not open sfz files in spite of the name. You had to go to the free sfz player if you followed the lineage.
The attack on vibrato is broken, nail in the coffin if you are trying to do steel guitar swells. They knew about the bug but no budget or whatever to fix.
Just a dinosaur. Glyn gave reference to a good and more contemporary player.
Good alternative dinosaur for sf2 that has all the bells and whistles is Jeskola. Paid a hundred bucks for this in it's prime. Now it is free.
Technological limitation is that it cannot deal with wav samples over 16 bit resolution. Otherwise, a much better alternative to SFZ+. Has all the features and overall a better machine. Such a loss that these guys didn't develop further.
https://jeskola.net/xs1/ John