Is it ok to clean with soften water and sterilize in RO water?
You can clean with softened water, it might make things leave less residue if you have really hard water and your cleaner doesn't have something like EDTA in it to chelate.
How are you sterilizing? With a pressure cooker, minerals in the water might leave a little buildup, but I wouldn't think it's a big deal unless you are using something like a commercial sized autoclave.