From what I've read, the main things that are going to change the body of your beer are your strike water ratio and the mash temperature. The type of water shouldn't change the consistency assuming the same amounts. Now, mixing your water will give you a different water profile, but the rule of thumb is, if it tastes good, it's okay to brew with.
Regarding full vs. partial boils... I would say that a full boil is the best option if you have the capacity to do so.