Its late and not everyone is a night owl so responses maybe thin at this time.
If you are interested in a G&P M16 with a RAS, I can confirm that G&P does produce atleast one.
I would choose G&P over Echo and KWA, but that is a personal choice based on good previous experiences with G&P.
Just because you buy the best of something does not mean it will negate all possible problems. If something is not installed properly or aligned properly then you could have issues. A person an drop 300 dollars of quality parts into a mechbox but if its not shimmed properly then it doesnt really matter how much the parts cost. If possible on your next build avoid bearings, if possible stick with bushings.