It's a bit unfair to compare Idoling episode to Mechaike, the scale is totally different. For what they are Idoling I think is a very entertaining show in their own capacity.
I also don't think Rino is that type of person in real life, she was in a character and played it well, if it wasn't for her the whole episode would've been lukewarm.
Super Girls is actually in good terms with Idoling as well, Serina is friends with their leader, not to mention Yurikaru and Ruka are also from Avex and know each other very well. If anybody is an outsider from this ensemble it would be The Possible, but they have been around for a while and clearly knows how to act in a variety show.
Was it scripted? Maybe, because I saw the two Super Girls unable to conceal a brief grin when Kikuchi scolded at them to stop whining and come out to the court. If they were really upset they wouldn't be smiling at such a moment.
In a way I'm glad Maeshima Ami wasn't there because she would've been REALLY ANNOYING.
Kikuchi declared E-Girls as the rival of Idoling, of course in jest during TIF.
Passpo and Super Girls are rivals because they both have the star symbol in their names.