I am in the process of migrating to Yellow, my experience is that if you are running the latest version of HA there is the ability to backup ZHA and restore to the yellow. The issues I have experienced with this are the devices / entities are renamed to a standard format so if you use custom naming conventions for your devices/entities they may not survive the migration, this in turn breaks automations. I am also having issues with Aqara battery operated devices like leak / magnet switch / motion sensors which have not connected and then when reconnected drop off again.
Note Yellow does not have a ZWave capability built in, only Zigbee.
A little more on the issues can be found here HASS Yellow migration - points to watch for (MQTT, Zigbee, restore)