regionprops won't measure anything less than 1 pixel so I'm not sure how you're getting 0.1 pixels for the area.
I'd recommend leaving your image as integer if you can, or leaving it as whatever floating point range it has if you can. If it forces you to scale your image to 0-1 with imdouble, then you'll have to unscale it later. But again, I'd prefer not to do any scaling at all - I rarely do, but then I've never tried to send in a floating point RGB image into regionprops to get intensity information (MeanIntensity). Of course for spatial measurements (area, perimeter, equivdiameter, etc0) you don't need to scale at all since measuring those is done purely from the binary image, not from the grayscale image (single color channel).