I just ripped out my insteon system and replaced it with Caseta. I wanted the "device-to-device" response speed.

It doesn't work unless you want those MadKatz looking remotes on your wall. The two button remotes send all linked devices to full power, so I process them in Home Assistant. Home assistant is fast enough to process the commands, but the lutton protocol doesn't have any sort of acknowledgement on the wireless side, it just keeps on blasting for 1.4 seconds. Good for reliability, awful for latency.. So for 1.4 seconds after an action, the hub waits for the first device to stop transmitting before it sends commands to the rest of the devices.

I'm going to try some "scene" remotes and maybe get it to be acceptably quick but there are still limitations.

ZigBee is so good, they made thread. Z-wave is so good, there are 4 versions. Matter over thread is what I wanted but that's vaporware for now. Considering what I know now, I would probably have gone with esphome or tasmota dimmers. I was worried about them mucking up my wifi, but they're the only things I have on 2.4 and the scene controllers and garage controllers have been solid.