Just looking around for an answer to this and I've found the following:
On this answer to a previous post, Luke indicates that from the ArcGIS Help:
The Raster Calculator tool is intended for use in the ArcGIS Desktop
application only as a GP tool dialog box or in ModelBuilder. It is not
intended for use in scripting and is not available in the ArcPy
Using the finest resolution possible is not neccessarily the right choice when doing habitat modeling. I can't think of any papers to cite right now but consider this:
When creating a habitat model (HM) the resolution highly depends on the species you are looking at. A mouse has a very different moving and cognition range from an elephant. Thus, using a 1x1 ...
Yes you can use Weighted Sum since your weights are decimals and as long as the total equals to 1, so there is no problem.
I will quote from the help above:
A useful way to add several rasters together is to input multiple
rasters and set all weights equal to 1.
Input rasters can be integer or floating point.