Mounting it directly behind the light isn't a good idea. Too much chance of that light blinding, even temporarily when the light is turned on. I'd go no further back than the light, keeping it on a center line of the light either to the left or right of that light.
Try mounting the camera temporarily at the edge of soffit to prevent IR light reflection or adjacent to the recessed light. I get that you want to avoid perhaps fading of the dome plastic from the suns rays. This way you avoid making unnecessary holes.
My preferred mounting method is to use aluminum flat stock. I cut a piece long enough to span the full width of the soffet from "wall to wall". I add a couple of ears cut to match the diameter of the camera base when added to the flat stock and use a piece of scrap aluminum to mount them to the flat stock. The flat stock gets drilled with a 1" hole in the center and drilled and tapped for mounting screws. The assembly then gets scuffed and washed with dish soap to remove the aluminum oxide, two coats of aluminum primer and two coats of semigloss to match the soffet color.
By locating the camera carefully the cable can be routed behind the flat stock and in a groove of the soffet to get into the attic, but it may be necessary to remove a piece of soffet to do this. The end result is a clean, stable, mount with no holes, at all, needed in the soffet. Removing a piece can be a bit of a PITA but the end result is worth the effort.
I think that is a full time color camera. If the lens cannot even see the light or anything reflected closely off it I think you’ll be just fine. You could test with a temporary mount—eg tape the camera to a thin piece of ply that is wedged between the flashing across the soffit.