It looks like that is a direct mount, no plate required. Do the factory sights co witness?
Yes, they co-witness well. As I said, I'm still learning to use the red dot, and have to sometimes rely on the irons, though I think I"m gaining ground on that.
Last night, I shot a local match, and had the red dot dialed down pretty low. I couldn't find it for the first stage of the match. Between stages, I went to the "safe area" and dialed that sight WAY UP bright, and had zero issues for the next two stages. In fact, I did pretty well for an old man. I just had the sight too dim for that first stage run. That's on me.
For the record, I like a single-stack pistol a helluva lot better than the double-stack pistol, but to be halfway competitive in today's USPSA matches, you've gotta have a double-stack, high-cap pistol, or you're screwed.