Around a year ago Stephan from CNC Kitchen on YT did a bunch of scientific tests to show how to best bond layers and attempt to print without inclusions. Maybe check that out. It requires higher temps and super dialed in squish. Printing perfect PETG requires double the amount of tuning and effort as PLA. It also sucks up moisture to the extreme. Like you can print fine with kinda wet PETG, it will make lots of zits, stringing, and terrible seams. If you want it perfect, the stuff has to be dried to the extreme and printed from a drybox. I hate PETG. I’d rather print any other filament if I can. If I really need to use it, I dry it, but I also manually place every single seam on the inside of my part and in the middle of any back walls. Almost all issues with PETG will occur due to or around seams. If you can hide all of these, the outside of the part can look nice. Like I’ll go into my design and add a tiny chamfered groove in the outer surface if I have no choice and must have an external seam. Just forcing the extrusion anchor inside the part by a few millimeters can help mitigate the issues. All the problems are due to moisture expanding and causing ooze combined with PETG being extremely sticky when molten.