Settings depend on what I'm printing. Heck, on some prints I even use active cooling. That said, I've always used 1.0mm for retraction. I think the big thing with PETG is that you shouldn't go too fast. Haste makes waste, don't you know...

My default printing speed is 2450mm/min, but I usually run the first couple layers at 75% of that and am a lot happier because of it..I couldn't tell you the last time I had to tear off a print and start over (knock on wood), except for a reel of some horrible stuff from a different manufacturer (ESun doesn't have PETG in Silver, the other mfgr did and was it ever crap).

Any setting it particular you're asking about? Just keep in mind (I sure do), that what works for somebody might not work at all for you. Ambient temperature and humidity come into play. How dry your plastic is comes into play. Etc. Etc. Etc...