My experience with the old formulation of Simple Green caused my fingers to split open with wounds that lasted weeks.  The reaction was not immediate so the cause wasn't easy to find.  For corrosion issues, I recall the US Air Force stopped using the original product and when we heard that, my own coupon tests did show corrosion as well.  I have not used the newest Simple Green.  I have Zep Aircraft Cleaner but that is very alkaline and still requires caution and thorough rinsing and Zep advises using pH markers to confirm the success of rinsing.   That should tell you something. I only use that on the toughest exhaust areas by hand spray.

Simple Green wrote that brief exposure and proper rinsing is not a risk to GA users.  I think that applies to almost all the products mentioned here whether purple, green or citrus.  Casual spraying and cleaning by hand is not a big risk from what I've read.  The problem comes from repeated pressure washing and having those solutions forced into bearings and into areas such as rivets and metal overlaps where the rinse would not reach.   Never pressure wash is a safe rule.  And, if you pressure wash weekly, you will likely have problems 10-20 years down the road.

My cleaning process uses dish soap and water for the majority of cleaning (turbine and piston) targeting a 2x2 foot area at a time.  I use the Zep for the greyest exhaust on the belly of the Legacy (after too many hours between cleanings).  My hangar mate typically cleans his after every flight and it is a simple wipe down for him with a household spray cleaner.