I totally agree with the burden of consistenticy on social media and I struggle with it too...

On your three questions:

• Steemit I use most, followed by IG and followed by twitter. I'm not a big fan of any social media and I haven't really posted on IG or twitter in like 10 months so Steemit would be my favorite by that metric.
• This is a tough question... I think some type of update to the trending page to make it a spotlight or something that isn't just whales would be helpful.
• I don't use spotify or iTunes...