so where do gender ergonomics come into play in a backpack?

Didn't you know that the "wo" in "women" is latin for "small" as in small men. That aside: https://www.rei.com/learn/expert-advice/backpack.html

Women-Specific Backpacks

Because they have smaller frame sizes, women's backpacks often work
well for young backpackers of either gender. Torso dimensions are
generally shorter and narrower than men's packs. And hipbelts and
shoulder straps are contoured with the female form in mind.

Also check shoulder width with respect to shoulder strap placement and sternum width.

Additional Backpack Fit Adjustments

Load Lifter Straps

These are stitched into the top of the shoulder straps, and they
connect to the top of the pack frame. Ideally, they will form a 45°
angle between your shoulder straps and the pack. Kept snug (but not
too tight), they prevent the upper portion of a pack from pulling away
from your body, which would cause the pack to sag on your lumbar
region.

Sternum Strap

This mid-chest strap allows you to connect your shoulder straps, which
can boost your stability. It can be useful to do so when traveling on
uneven cross-country terrain where an awkward move could cause your
pack to shift abruptly and throw you off-balance.

Edgar, this is a good link. Thanks. So, hips and shoulders are also taken into consideration.
It would be helpful for on-line pack definitions to discuss more than height, width, depth measurements. Some range of adjustments would help.

If I could, I would try in store, but good choices are hard to come by here.

I got my daughter a North Face women’s backpack during REI bi-annual sale. One really nice feature is the straps have curves that take into account that women have breasts. Makes for a really nice fit whatever your boob size.

Thanks for the brand recommendation. Yes, bust and hips need to be taken into account, but as a plus size 5'8" woman with a longer torso, I am thinking no woman's design is going to accommodate my particular shape.
If only we had more store front shopping options for these often recommended packs. I do recommend people 'test drive' and measure luggage in store, but packs are hard to get here.....and Canada does not have the generous free shipping and return policies of the U.S. so efficient and affordable decisions are harder to make at times.

If the backpack does not have a decent hip belt to lift and transfer the weight to the hips, a person with a short torso, male or female, should buy a shorter backpack. In the old days when travel packs were much larger and carrying-on was not as common, there were a lot of short travellers with large backpacks, without hip belts, hanging off of their shoulders with the bottom of the pack down past the person's butt sometimes banging the back of their thighs.

If your backpack has a decent padded hip belt, a taller or longer backback should not matter in my opinion. In fact it can be an advantage. If you lift and transfer the weight to you hips, ideally it should reduce the weight on top of your shoulders. If you examine a large technical hiking/expedition pack (some lengths over 36") with a suspension system, the top shoulder strap attachment should be adjusted several inches above your shoulder and the shoulder straps only put pressure on the front of your shoulder or chest and serve to keep the pack from flopping off of your pack. Most of the weight is transferred on the hips to permit you to carry heavy loads for long distances or time. If the top attachment point of the shoulder strap is adjusted to be level with or below the top of your shoulders, then some weight is transferred on top of your shoulders. IMO, it is better to be longer than shorter.

Because of maximum carry-on restrictions, I am of the opinion that current travel packs are too short for a lot of people. I am 5'11". My travel backpack is at the maximum carry-on size of 22". If i adjust the hip belt to ride on my hips, the top of backpack is at or just below the top of my shoulders. That means a significant portion of weight is still on the top of my shoulders. I can loosen the shoulder straps but then the backpack will flop a bit off my back. Or i can lift the hip belt higher, but then i am cinching it tight on my abdomen and the belt is riding higher and off the hips. So in my opinion a shorter person should find that the carry-on max sized 22" pack to be more comfortable than a shorter so-called "women's" backpack. If you have large boobs which require specially curved shoulder/chest straps, prefer fuchsia-coloured materials or choose to stuff the men-sized pack to an unbearable weight for your abilities, those are different considerations.

you need to try backpacks on - fully laden - and decide which is the most comfortable, anything else is just waffle

It would be helpful for on-line pack definitions to discuss more than height, width, depth measurements. Some range of adjustments would help.

Rather than pack specifications I would depend more on actually trying on packs with load. This is where "brick and mortar" has an advantage over mail order.

Some packs have minor adjustment capabilities with respect to strap attachment points. REI resource: https://www.rei.com/learn/expert-advice/backpacks-adjusting-fit.html

Found on a lot of packs, adjustable suspension enables a pack to fit a
wider range of torso lengths and to more precisely fit individual
users. Different brands use different systems, but most of them are
fairly intuitive. If you buy a pack with this feature, torso length is
your first—and most important—fit adjustment. Adjustments happen in
two primary phases:

The Main Event: shoulder straps/hipbelt

The Finale: load-lifters/sternum strap

In addition, because fit adjustment is a dynamic process, experienced
hikers continuously work to relieve pressure points by fiddling with
the tension in their straps (the encore).

I like for the base of a loaded pack to rest in my lumbar area. Pack size matters. A 65 liter pack is for backpackers carrying tents. Most travel packs should be around 35 liters for casual, Summer type travel.
As a woman - I really need a sternum strap that can be positioned close to my neck due to my chest size. Or, I need to avoid a sternum strap altogether.
As mentioned above - padded, curved shoulder straps are important to me as well. Picking out a pack can be as personal as finding comfortable shoes.

Thanks for the recommendations. As said, it is not easy to find the bricks and mortar stores that sell good packs here, but the comments and fitting references help me review the fit of my past pack...a unisex MEI Voyageur. At one time the recommended bag by the One Bag website. There is a lot that is good with it, but though carry on compliant, it is still too big at 43+ litres. As it fits well, I am thinking a man's bag would fit my shoulders best, but with an adjustible front strap for the bust, and adjustments for back length.

While I haven't been to Ontario, Canada I have been in MEC stores in Calgary and Victoria. If you can get to Toronto there is a MEC at 400 King St W, Toronto, ON. The MEC stores seemed to have a large selection of outdoor items.

Edgar, I have a MEC across town, and a SAIL nearer, but neither carry the designs I want. MEC does now carry Eagle creek, but this is very recent. Often their selections are for hiking packing and too many exterior pockets for my travel method (every zipper needs to be lockable). Thankfully, websites let me narrow down and check regularly. Perhaps Global Companion will arrive in town eventually. Motherlode, most likely never.
The recommendations and tips have been very helpful. Thanks.

I'm not sure of the availability in Canada, but you might take a look at Deuter packs. As a short, plus size woman I had a hard time finding the right pack fit also. The one I had was very customizable. The shoulder straps could be adjusted up and down as well as the hip belt. This made it easy to adjust down to my shorter torso. I hope you find something that works!

I'm on Patagonia's email list and got an announcement about women's specific packs:

http://www.patagonia.com/product/womens-nine-trails-backpack-26-liters/48440.html?dwvar_48440_color=STRB&utm_source=em&utm_medium=email&utm_campaign=042018_trail_packs&ett=1704839624

Women specific features include:

Women’s-specific harness and back panel

Padded shoulder harness with adjustable sternum strap and waistbelt
for secure fit

Available in two sizes: S/M, L/XL