You don't HAVE to get the Companion to connect two Honda generators together in parallel.
All you need are two generators from the same model family (i.e. two eu2000i's) and the parallel cord.
The limitation of two "normal" eu2000i models in parallel is that the maximum current you are supposed to be pulling out of a regular household plug is only 20 Amps.
The Companion model has a 30A twistlock plug that "lets" you draw the full 26.6 Amp output from the two generators in parallel. That is the ONLY difference!
All you need is a twistlock to RV plug adapter, and you can plug directly into your RV and run just about everything.
Get the Companion model.