The smart remote does still output infrared codes , so you can control the older boxes.
However you can't connect the smart remote to the older boxes so all the clever remote functionality will not work - controlling box with radio frequency codes, voice search, and the ability to control TV power + volume.
Here's my findings if using the smart remote with the older NowTV Smart Freeview box (where the std black box would be the same apart from you don't need the WOL App or original remote to start up the std black NowTV box).
It's been a long time since i tried the nowtv stick smart remote controller on the NowTV Freeview box.
Where the newer smart remote controller does operate the NowTV Freeview box to a certain degree, but there is some big caveats with it.
From memory, you can't switch on the Freeview box from its deep sleep mode and need the original remote controller that came with the box or use a WOL App on your smartphone or have to unplug and replug the power to the box to kick start it into life.
I am not sure that if you factory reset the Freeview box if the newer remote controller will work when setting up the box again.
The voice search button feature will not work, none of the direct short cut keys work apart from the Sky Store button.
Personally i wouldn't consider it and stay with the standard infra red remote controller that comes supplied with the NowTV Freeview box (even if you like the idea of the TV on/ off standby and volume TV adjust buttons on the newer smart remote).
Forgot to mention a vitally important bit of information that you need a NowTV Stick or NowTV 4K Smart box to initially setup the smart remote so that the infra code commands for your TV on/ off standby and volume adjust buttons on the smart remote controller to work with your television.
The older boxes haven't got this functionality in their software to program the smart remote controller.