Okay, buckle up for a science dump, since you asked.
There aren't any proper studies on KLOW or GLOW in humans or animals.
BPC 157 has had a few small human trials (arthritis, cystitis, basic safety). Most research is from one small group and seems a bit suspect. DOI: 10.3390/ph16050676. They seemed to overstate its effectiveness. No real research anywhere else.
GHK-Cu has been tested on humans, but only on the skin, not injected or taken orally. It's not being developed for full-body use.
Thymosin beta 4 is being tested in humans after heart attacks, and for basic safety.
KPV seems to be mostly researched as nanoparticles for ulcerative colitis, far from human trials.
These peptides definitely do *something* in the body. The problem is, they're hard to patent, so companies won't fund research. Drug companies want compounds with one specific, well-understood effect so they can predict the results and avoid surprises. Most of the peptides in KLOW have broad effects on many systems, and we don't fully understand them. Studying all these effects would take a ton of research *before* human trials.
Just because something works in the lab or on animals doesn't mean it will work on humans. There are tons of Alzheimer's treatments that work on mice, but they've all failed in humans.
Many people online say it helps with healing, which is interesting, but not proof. Before science, people believed in all sorts of weird treatments. (Leeches, anyone?)
The biggest concern is that many of these peptides affect growth signals and angiogenesis, which could potentially cause tumors. They're not likely to be developed as drugs, and I doubt anyone will test KLOW on humans due to the complexity and unpredictability of its effects.