Hi Seb,
thank you for your requests.
Regarding the first one, if the image is out of focus, in mostly cases it won’t be aligned and you should see it with red frame. I suppose it is not possible to delete such image after that.
Regarding the second one, you can basically use any images in RealityCapture. Or do you mean you already have some scan in RealityCapture and you want to add another images there?