I think Rengo shouldn’t be considered too seriously, for me it’s a way to have fun with friends and/or a teaching tool where weaker players are confronted with better moves from their partner or opponent.
A few years ago I played a Rengo (with handicap) as a 9k, the three other people being 1d+. My opponents tried to drive the game into complicated positions while my partner kept trying to repair my blunders…