I've noticed that it does float around a bit more when engine is warming up. Still, normal. Do clean throttle body every once in a while and it will limit dirt's effect on making the issue worse while idling.

Normal. The car idles very low when warmed up, any sudden added strain (AC, fans, and rear defroster) will slightly drop the idle. Even as the AC clutch cycles automatically or cooling fans turn on, it will drop the idle.

I had the same symptoms, AT, 2013, would dip almost to a stall when coming to a stop. I doubted the spark plugs or coil pack. A week later, symptoms of a weak battery showed up. And strangely, when I changed the battery no more dip when coming to a stop.

My manual FR-S has the same behavior when coming to a stop from highway speeds, when in neutral. But, by stall it was around 500rpm.