I've also been reading a fair bit about the soil food web and what really strong fertilizers end up doing to that web(basically upsetting the ecosystem and it collapses).
In potted plants, it's perfectly fine because we usually aren't relying on the soil food web to support the plant so synthetic or otherwise... slapping a shit ton of nutes, as long as the plant can take it, is perfectly fine.
When you see 15-30-15, vs 3-6-3, it's simply the concentration.
When you feed, you should pay attention to ratio (including micro nutes), and EC/PPM (total amount of nutes).
Plants like certain ratios. For soil grows, the best I can come up with for cannabis with all my research is that they generally like 3-1-2 or 2-1-3(lots of evidence for both) during veg and a 1-2-3 for flower. Some say that after the first 2 weeks of flower you start reducing the N. It's said a ton, but there is more consensus over the years on the 1-2-3.
Warning: This is my personal sense, given all the information on the various growers forums and youtube videos I've consumed...
Also, plants can only take in so much before they start hurting themselves. Don't let them snort the whole bag... little bumps with water between