Haven't used either of those apps myself directly, but from a few quick searches online they look to be doing the same job. It's probably a matter of settings - even when I had Qsynth and Jack running right, I had to go into Jack and align the audio streams etc and fiddle around a bit. Qsynth was a bit better, just had to get one midi device working and it was OK then.

Online is stating that PipeWire is now the default instead of PulseAudio or Jack. From my understanding they both sit on top of ALSA, the audio hardware driver.

So for things to go right you need: 1) Cynthia directed to playback through a working midi input device (she has a playback device range of 1-10, or "A" for all of them at once) 2) The midi input device is synthesised by FluidSynth which takes Cynthia's midi instructions and converts them into wave audio output 3) The wave audio output is directed to PipeWire/PulseAudio/Jack Audio 4) PipeWire/PulseAudio/Jack Audio ultimately direct it at your machine's hardware driver/handler, ALSA, which directs to your soundcard/sound chip and out to your speakers/headphones if all goes well.

I've read online that Jack is the pro option, which is why it was so complicated to do the basics, and PipeWire/PulseAudio are a little more user friendly?

If you switch Cynthia's Playback Device to "A" (bottom right of main GUI), she will play/broadcast her midi notes/instructions to all available midi input devices simultaneously, so if you have at least one midi input device producing sound, you should get something coming through to your speakers/headphones.

Unfortunately, I can't offer you much more help than this, as I'm not familiar with PipeWire/PulseAudio, and as far as I know FluidSynth was controlled behind the scenes (under the hood) by Qsynth's GUI.