I think the new remote only has the ability to work with one other device. My Sony XBR-49-X800H has HTML-CEC capability, so it can operate other equipment via those protocols when properly set up. I set my new ATV 4K remote to work the power and volume on my TV, and then the TV uses its HTML-CEC connections to my Sony soundbase to control it. As a result, all I have to do is press the Power button on my ATV remote and it turns on my TV, which then turns on my soundbase and sets the ATV 4K as the device to use. When I change volume on my ATV remote, or mute it, the TV automatically adjust the volume on my soundbase. Pretty cool, and simple to setup if your devices are compatible with HTML-CEC. But it did require HTML-CEC. An older TV might not be able to do that.
The key to using HTML-CEC is to control everything with your TV. Then the TV can do all the work. If you set up you sound system to control the sound without the TV, then it will be problematic. My older TV didn’t have HTML-CEC capability, so I had to use the soundbase to send signals to every device, and that was a PITA. HTML-CEC greatly simplifies setting up an entertainment system.