Get the 12″. The bearings are actually pretty good, but the 12″ will be much preferred over the 8″.
We stack 2 karts and stands and other stuff on our 12″ and cruise 75mph with no worries. Regular bearing inspection and re-grease will keep it all happy.
Note: Ours stays in the garage. Not out in the weather.
My WRX probably has the hitch at a similar height as your Honda. The ball holder is just a basic one and the trailer sits level. You won’t have a problem with that, there are so many ball holders available.