Bob, I'm far from being an expert on this, JimD for example used to write a lot about it on this forum, but I'll give it a try. Note this is heading OT fast, there were some threads for this if anyone can dig them up.
Define BAU as business as usual = we do not need to change our lifestyles. Economic growth, A/C, vacations in faraway places, big homes, cars, meat, having as many children as we want, no limit on personal wealth, etc.
Black BAU - what we have today, fossil fuels based BAU.
Green BAU - how to achieve BAU while avoiding climate change. Supposedly, through technological progress, renewables and EVs becoming so cheap and compelling that the entire globe is converted, we are saved without serious pain and sacrifice.
Some of the problems with Green BAU are its speed, too slow considering where we are already, and its lack of full coverage (agriculture, cement, flights, population beyond carrying capacity, and all the rest of the unsustainable bunch). It also lulls us to sleep believing all will be well. Its biggest advantage - not a lot of backlash, it's highly marketable. Plus it's progress in the right direction even if it doesn't save us, as you explained well a few posts back.
Real Green - how to actually avoid catastrophic climate change, and avoid an uncontrolled population collapse, but giving up a lot of privileges we are used to, "cutting out the fat", with a WWII-style (or worse) joint global effort. Biggest advantage - it could work. Biggest drawback - it will not be adopted unfortunately