There are several fluid plugins and each one behaves differently.
You are using sfizz correctly. But the behavior in sf2 is not the same as in sfz. Each Sfz defines an instrument and variants of it. An Sf2 defines entire libraries.
Let's get to the point:
If it is to be used directly on a midi track and not on a bus, I recommend FluidSynth DSSI.
To avoid problems:
1 Load the sf2 library from the plugin interface (do not select the instrument, leave it as default, otherwise the conflicts you mention may be created.)
2 The instrument must be selected from the track properties.
There are several fluid plugins and each one behaves differently.
You are using sfizz correctly. But the behavior in sf2 is not the same as in sfz. Each Sfz defines an instrument and variants of it. An Sf2 defines entire libraries.
Let's get to the point:
If it is to be used directly on a midi track and not on a bus, I recommend FluidSynth DSSI.
To avoid problems:
1 Load the sf2 library from the plugin interface (do not select the instrument, leave it as default, otherwise the conflicts you mention may be created.)
2 The instrument must be selected from the track properties.