Is the Polyend Synth “more compatible” with the Play Plus over other external synths. Is it pre mapped or have other special advantages as the top choice for an external synth to work with the play +?
Synth accepts MIDI messages just like any other device, so it‘s not more or less „compatible“ with the Play series of devices.
Having a premapped preset may also not be desirable, because there is so many possible destinations that most likely you‘d like to choose them yourselfs anyway.
If there’s a common set of destinations you like to use, i’d personally would just create a template project with a default mapping and save it, so you can reuse it anytime you want. 