Short answers to the questions the product pages raise. Longer pieces are in the journal.
The three spectrum words
Full spectrum keeps the whole plant including up to 0.3% THC. Broad spectrum keeps the plant and removes the THC. Isolate is CBD and nothing else, usually 99% or better.
Reading a label
Two numbers decide whether something is worth buying. Total milligrams in the pack, and price per milligram. The first is usually printed. The second usually is not, which is the point.
Reading a certificate
Check that the batch number matches your bottle, that the test date is recent, that assayed potency matches stated potency, and that there is a contaminant panel and not just a potency figure.
Cannabinoids other than CBD
CBG appears in daytime formulas. CBN appears in night formulas. CBC turns up in full spectrum extracts without being added. None of them is a miracle and all of them are tested for.