Last time I had blur issues with RTs they were acrually due to engine bugs and the screencapture not ignoring the athmosphere/athmospheric fog.
So there is a possibility for that to still be the case as well.
Additionally.
Behind the current camera is the closest spot you want your stuff to be.
Its outside the fustrum. Invisible in game anyway, and only visible to the RT.
where you place it doesn’t really matter. May as well be linked to the player.