pin to axle length vs wheelbase

do i care if the pin to axle length of my trailer is shorter than the wheelbase of my tow vehicle? how do i measure pin-to-axle length, ie to the center of all (both) axles or to the front axle only or rear axle only?

i understand that a longer trailer is easier to back up but is there a critical ratio where i should start to get concerned? i am going to be restricted to getting a relatively short GN trailer (32' overall) but if I can get away with the long bed truck I'd like to do that.

I don't want to be frustrated every time I try to back down the driveway though. Hard enough getting the 18' tag down in one go.