I jumped from SmartThings over to zwave2mqtt.
I wanted to try out OpenZWave1.6+, so I built both from their source. ZWave2MQTT requires NodeJS in order to build it from source (as well as run it) and this takes a bit of work. I moved over all my devices from ST to z2m. I’m happy with it 
. But I would say z2m is not for everybody as I mentioned it takes a bit of work to get z2m going w. 1.6.
I can’t really comment as to whether z2m will help you out as my ST based system did not have instability problems. ST did have a few quirks in implementations to bridge over to HA and it did have delay problems but that was due to going to the ST cloud and back too many times which was my main motivation for changing.
Here is another thread you may want to explore: