Achieving high-quality results through synergy has not been well documented, so it's really hard to give you a straight answer. There is also the issue of recording energy levels and (possibly) impurity ratios if one were to try to figure out something similar to tiers in regular crafting.
In my experience, seeing a high-quality result is much more common in Synergy than regular crafting. When I was experimenting with apple juice at level 0 synergy, I was still able to obtain high-quality results. I had no problem adding high-quality slots to the ebon gear back when it was first released. In the end, I found energy levels to be the most important factor in high-qualitying whatever I was trying to make.
Signature starts here.