NO you do not want to tie the white and orange together.
Yes...you can turn both electric and propane on at same time for faster recovery.
ANY water heater with both electric/propane can do this.
Yes......this water heater is a replacement for your old water heater in that it is a combo (electric/gas) and will fit in same opening.
But it does require new wiring scheme due to design changes.
120V AC needs to be wired to/thru the box with relay. Relay is DC activated which allows AC to element when a 12V DC ON/OFF Switch for electric is turned ON
Propane uses 12 DC and will light off when a separate 12V DC ON/OFF switch is turned ON
BOTH electric and propane use 12V DC to/thru circuit board in order to function.
You could just wire propane circuit....all wiring is already there.
And deal with electric wiring when you have proper time to do it correctly.
