Really anything besides a group could be subject to the popcorn effect. I don't know of any Z-Wave bulbs that support groups (700 series devices should help with this, but I'm not sure any bulbs are on the market yet). Zigbee does, but Hubitat doesn't let you use "Start Level Change" on those. To me, that really leaves only Hue groups over the LAN to a Hue Bridge where they are grouped (via a room or zone in the Hue app), but even that isn't so simple since Hubitat's built-in Bridge integration lacks these commands for group. It's one of the reasons I wrote my own.