VPATH is something that RXP/GTN provide, it isn't something we have control of. I'm not totally sure on what you are asking on it, but that would be something to talk to them on. The DFC90/Entegra won't automatically fly the VPATH.
X-Plane currently doesn't have any weather radar APIs available, thus isn't a method for drawing that.
Rain should depict on the windshield, but X-Plane 12.1 did make some changes to that system that are yet to be integrated. The fleet will be getting 12.1 updates over the coming weeks and months