In my experience, no 1 way to choose when to harvest works for all plants. I generally see plants fall into 2 categories.
1) If they fatten up fast with clear trichomes, i wait for the trichomes to get cluody, then harvest, but also a time limit on how long I wait after the calyxes are fully plump.
2) If they fatten up slowly and the trichomes start to get foggy and even some amber before it fully fattens, I'm harvesting when the calyxes get fully plump even if i get a little extra amber than normal.
Calyxes need to be full or else the buds will shrink more than normal. I also don't want to fall into the trap of a plant that doesn't get many amber trichomes and let it over-ripen. The THC in the trichomes may not be breaking down, but the plant material doesn't taste as good when it is over-ripe, in my opinion.
I'm also paying attention to the lower buds. If you don't torch the colas, the deviation should not be too great. If you torch the colas, the lower buds will be even further behind than normal lag from top to bottom. While i pay attention to them, I will not sacrifice quality of the best buds on the plant for the worst buds on the plant at the bottom. They are a factor but a less important factor.
Trichomes are probably the best thing to pay attention to, but the longer i grow the less i rely on them. I care about the trichomes, the pistil color and density of buds. If 1 is not a normal progression, i rely on the other 2 more.
Be systematic so you can try new things and compare the results in a meaningful way that you can repeat if you like the adjustments you make over time. Try not to change too many things at once. Regardless of any suggestion, your personal preferences as far as early-to-late harvest window may be different than others. there's no 1 right answer, but there is a range of common sense options.