The auto start is very easy...just order the Onan optional auto-start for the QG4500. It is plug and play...route the panel where you like.
There have been 2 types in the past (set for voltage or voltage and temp for AirCon). Get what you need.
The inverter is a more complex topic. The factory Xantrex1800 is OK, but not available on the 31E, feeds only the TV and 1-2 outlets, plus it is modified sine wave...so not the best for sensitive gear.
You can add point of use inverters as needed, add an inverter to the outlet circuit with auto transfer, or add a whole house inverter...as you see fit. Lots of options there.
We added a whole house like this (only much bigger at 2000W/3000W peak)...very easy DIY:
Kim and Steve, Mustang LCDR (Ret), '07 Damon Outlaw #1193
I have seen gross intolerance shown in support of tolerance, Samuel Coleridge
WE LOVE OUR OUTLAW RV