Migrate from Domoticz using MQTT

I’ve almost decided to move from Domoticz (running on old Pi 3 with Z-Wave.me daughterboard controller) to HA (running on Pi 4 with SiliconLabs SLUSB7000A USB stick) but have not been able to get the SL stick to locate any Zwave devices further away than a couple of meters. The old Z-wave.me controller however has no problems with devices being 50 meters away. Well, I have to assume that SL will be able to get their sh… together and make a driver that works one day.

In the meantime, since OpenZwave seems to be a dead end, I’ve installed Mosquitto MQTT and Z-Wave-JS on the old Pi 3 and have that working more or less ok.

My question is would it be possible to configure Z-wave-JS on the new HA to use the Mosquitto MQTT on the old Pi 3? In theory I should be able to just select MQTT gateway, set correct hostname/IP-address for the Pi 3? What settings should I have on Retain, Clean, Store and Auth? What about Gateway and Home Assistant settings? I assume WS Server should be off and MQTT Discovery on? How about Discovery prefix which is set to homeassistant on the Z-wave-JS on the Pi 3, should that be the same on the Pi 4?

I’ll end up with needing 2 Pi’s for a while, but when SL makes their stick work I should be able to transfer control from the old controller to the new?

Lot of questions, but hopefully there is a lot of folks out there that knows much more on this topic than me.