First of all, I would never put Simple Green on a guitar. Especially a fretboard which is open grained, non-finished wood. They can tout it as "organic and natural" all they want, but it's chemicals and it's formulated for "washable surfaces", which I would probably interpret to mean non-porous. It's main ingredient is a type of alcohol. It also has colorants and fragrance and I'd be avoiding those as well. Does your fretboard get that dirty that it needs a heavy duty chemical cleaner? I use 0000 steel wool with the grain which takes off all surface dirt and grime and it also polishes up the frets. I would think you could also use NAPTHA on the fretboard as well, or denatured alcohol as well. They both evaporate fairly quickly. I'm sure others will chime in on this, but I wouldn't use Simple Green on the fretboard! Sounds like a bad idea to me.
As far as Martin, Gibson, and Dunlop products, it has been reveals numerous times on this forum and elsewhere they they contain silicone which should be avoided at all costs. The Meguiar's line of products that are labeled as "Paint Shop Safe" are good. That means that they have no silicone. But some of their products do. Read the label.
The StewMac Preservation polish is a good one, as are the Virtuoso Products.
My general thoughts on polishes and products for guitars is, less is more. Keep it simple. You don't need a lot of product on your guitar.
I'm sure other opinions will be forthcoming.