The kit would tap into the power beyond coming out of the loader valve before it gets to the three point hitch hydraulics.
Theoretically, you could install as many rear remotes as you like, but the first valves in the system always have priority.
The steering always gets first dibs on hydraulic flow, but it doesn’t really rob from the rest of the system. Then the loader valves, then rear remotes, and last is the three point.