Another issue is that backplates in environment overrides, don't play nicely with ACES OT or LUTS etc, and the tone mapping control rarely works to reverse the effects. So if using any tone mapping techniques in the frame buffer, then its pretty pointless getting your backplate looking how you want it to in your photo editing app beforehand, as it rarely looks like the same in render.
If you process backplates as you would a normal photograph and then use it in Corona with any sort of of Lut, ACES OT or tonemapping tweaks, you'll effectively be applying two tone curves to the backplate (one in Lightroom, one in corona) and one to the render. Giving a mismatch.
I'm currently experimenting with processing backplates using Linear Profiles and using them that way, almost akin to prepping a proper Albedo texture. That way the only tone curve being applied is in render and theoretically the backplate should align with the rest of the render in terms of 'look'.
Quite often we capture full 360's on site to use as reflection overrides and/or direct visibility overrides - but as already stated, Corona in it's current state doesn't really cater well for any workflow involving jpeg backplates in render.