I've looked for studies that directly quantify this and can't find them. I'd certainly like to read them if others can.

What I do know is that, if you trust that report from 2017 that 100 companies were responsible for 70% of emissions, the best we could hope for, if all humans literally stopped using energy completely, is 30% reduction--which would be amazing, but obviously, we will need to keep using energy to survive, so it'll be lower than that. This study is old (10 years ish) but talks about how there's a floor in the US, that even someone who is homeless and eating in soup kitchens has 2X the global per capita carbon emission: https://www.sciencedaily.com/releases/2008/04/080428120658.htm

I think actually quantifying these things would be helpful. If we could show that getting X number of people to do X action would reduce emissions by X, we could focus on the highest impact actions.

Another important issue is that many 'green' options aren't all that green. Like a Tesla. They're green once they get into your hands, but weren't green to make: https://www.wired.com/2016/03/teslas-electric-cars-might-not-green-think/