Hi Wayne,
some things will only run on the left side screen, that is the weather returns, the coloured height map and the PLAN mode of the FMC. This is unfortunate but will likely stay that way for a while - we may revisit when X-Plane adapts Vulcan.
You can certainly display all other modes (VOR/LOC, MAP, CTR MAP, etc) on both sides, just use the EFIS control panel to do that. There is only one FMS computer in the 737, so both screens will always show the same flightplan.
Cheers, Jan