as I have mentioned, I've been challenging gyms, and I only got the 1st 7 in Kanto, so I haven't defeated Red. Steven hasn't appeared for me and I can't find Latios roaming Kanto... I'll focus on defeating Green and Red and inform you of anything I can.
But I kinda think Latios is exclusive to Soul and Latias is to Heart, although I'd preffer the oposite, since I'm getting English Heart