the new architecture will make it a bit quicker to load status.
Old architecture, apple just kept a list of smart home devices, each of your controller devices, like phone or Mac, would just pull that list, and act as it's own controller, so launch home app on phone, it polls all of your devices individually for current status, which leads to "updating" for a while as the reports come back. Launch home on your Mac 20 seconds later, and then your Mac will poll all devices indvidually for their current status.
New architecture, one of your home hubs will keep itself up to date with the status of your house, then when you launch home app on your other devices, it only has to ask that one home hub, and it will pretty quickly send status for the
entire house in one shot.
For control commands, I'm not sure if they still go through the home hub when you're home or not. I'm also not sure if when you play a scene, if the phone tells the HomePod to play the scene, and then the HP sends the individual commands, or the phone sends the commands directly.
as far as your individual smart home devices are concerned, both architectures the same. as the status request from the main home hub looks the same to them as a status request from your phone. and commands are also the same.
any OS older than last year's can not access the new architecture, so as long as you're iOS 16 or 17, Ventura, or Sonoma, it should work. This also applies to sharing, so you won't be able to share your home with anyone with an older OS . and any home hubs with older OSes won't be able to participate in your home. Don't think any of this applies to you, but just putting it out there.
