P180 EHSI control panels, how does it work?

Hi all,
i am working on a flightsim model of the Piaggio P180 avanti for a game (i.e. not real life training). I am currently trying to understand the logic of the autopilot, pilot and copilot EHSI and control panels and their relationships and can't figure out exactly how it works (i work from the POH only and have no real life experience of complex cockpits), so i have a few questions for this community.

I am trying to model a cockpit that has a Collins APS-65 (POH section 9 - supplement 1) and a Collins EFIS-85B (POH section 9 - supplement 3).
This means it has two HSI devices: one EFIS/EHSI for the pilot and one EHSI-74 for the copilot.
It also has two control panels: one DSP and one HCP-74 (if you can see the picture below, the top one is the DSP, the bottom one is the HCP).



On the DSP i can select:
- BRG (off, vor1, vor2, wpt, adf)
- CRS (off, vor/loc, lnav)
- i can also change the heading bug degrees and the course degrees

On the HCP-74 i can select:
- BRG (vor1, vor2, adf)
- i can also change the heading bug degrees and the course degrees

Questions (i know they sound silly but i can't figure out how it works from the POH only):
- when i change the heading on the DSP (or the HCP), is it reflected on both pilots EHSI or only one?
- how do i select the course source for each HSI, do i choose a bearing for choosing between Nav1 and Nav2? can they be different? (nav1 on pilot hsi, nav2 on copilot hsi)
- if this is the case, what source does the autopilot use in nav mode?!

Thanks in advance for any explanation (or url...).