As jokiin say.
There have been some cameras that had 2 memory cards, in some cases a regular SD and a micro SD ( lukas )
Not quite sure exacktely how thise 2 card cameras was working, i have a sneaky feeling the footage of the 2 cameras still ended up on one of the cards and the second card was solely for event / parking guard.
But today the standard seem to be 1 memory card that take care of it all ( cameras getting saved with the usual the date/time stamp + suffix A ( F ) or B ( R ) indicating Front and Rear cameras )
And then the RO ( Read Only ) folder where event files go and so also parking guard as its all events if there are any triggers.
In regard to the A129 which i have only heard about, then i do think its a worthy upgrade from your A119S, as i recall the sensors in play are the same, so it cant really be a step back with a extra camera.
On the camera screen you can get PIP wit the 2 cameras, but as its a small screen and the little PIP from the one camera will be < 1/2 a stamp size so really useless, i just have the front camera on the screen on my SG9663DC camera, but you can mix it up as you like.