Because bags are my jam, I will continue to go down this road with you.
Gregory and Osprey have similar mid to late 70's origin stories with the founders not being able to find what they wanted so they started making it themselves. Patagonia is in this realm as well.
What makes Osprey superior in my mind is the warranty.
Gregory-Lifetime with a whole bunch of "Exception, Key, Erasure" limitations language.
https://www.gregorypacks.com/warranty.html
V.
Osprey-Any damage or defect for any reason...
https://www.osprey.com/us/en/custome...ghty-guarantee
Moreover, Osprey is still privately held with original folks still in the mix. Gregory has been owned by Samsonite since 2014.
North Face, owned by VF Corp forever. Mountain Hardware, breakaway from NF, now owned by Columbia.
Patagonia, privately held, original owner still in the mix. Sometimes called "Patagucci" because of the MSRP on some of their stuff. Guarantee is solid but not as good as wait for it-----Osprey.
ALL of these bags, particularly in this sub 100 space are completely fungible. It simply does not matter day in, day out. Where it might matter is on the back end if you have a warranty claim.
AGAIN, you are stepping over dollars to pick up pennies on this. In this sub 100.00 space there are DOZENS of packs that will work just fine.
Some of your goals seem mutually exclusive. You want a pack with a base weight of under 2 lbs. That really maxes your total weight out at 15-20 lbs, particularly when you want no or a minimal belt.
You want to load the pack up and then NOT deal with sweat, in FLA because you think that there is some magic airflow design that will make a meaningful difference under load at temperature.
You want internal compartmentalization which often means internal zippers which means more weight.
You have been thru at least two packs so far (Vertx and and Alpha 19er) neither of which were appreciable better than the old trusty REI 25L bag.
IMHO and experience, the one brand that is a game changer in this space because built quality, feature set, durability exclusive use of Tier 1 components and well thought out design that I hear again and again is Tom Bihn. That bag for you is likely the Synapse 25. It is 220 plus shipping. Depending on fabric it is just under to right at 2lbs.
Beside price as being a potential deal breaker for you, the water bottle carry area is internal. I would respectfully assert that helps it stay a less hot because it is out of the sun. It also cannot be knocked out as it can from a mesh side pocket .
I acknowledge that you have to de-pack on the move and/or have somebody help you get the water bottle out on the fly or stop altogether. Frankly, you should stop and hydrate anyway. If hydrating on the fly is driving the train then they first thing we should be talking about is water bladder compatibility and that is an entirely different pack.
Looping back- You need a basic daddy bag to replace/augment the REI 25 you have. You say the Vertx and others are too heavy at 3 ish pounds. All things being equal, bags that weigh 3ish pounds carry more and more comfortably than bags that weight 2ish pounds.
You know the best way to not have to worry about the difference between a 2ish pound bag and a 3ish pound bag -IT IS BY BEING 1lbish+ LIGHTER YOURSELF.
Actually...Wearing lighter footwear on your feet is really the way to go as well as 1 lbish pound + on your feet is 5 ish on the back but that is a whole nother rabbit hole...
Look, I get it. My EDC bag is a circa 2005 Eagle Industries 3 Day Assault Pack. It is a bag of bags with a smaller bag containing a FAK, another with writing utensils, another with a flashlight and cords etc. I have an NWOT sling bag from Maxpedition, I never use. Why-because when you load it up, it is not as comfortable as any two strap bag. I have an LAPG Special Edition Maxpedition Falcon. It has more built in organization than the Eagle but is a bit too narrow for my laptop etc.
I have a Bright Teal/Green REI 25 L backpack when I travel because it coordinates with a Patagonia Duffel I have and I can spot that "set" 100 yrds away if it gets piled into a particularly place/room.
Hell, I even have an old school, 1000D cordura black Jansport backpack. I also have 5-6 other 35-45L carry on travel backs that may not be backpacks per se, but are 3 way (backpack/suitcase carry, duffel carry.)
Knowing everything I know now and I wanted to carry what you have said you have wanted to carry (moving goal posts and all) I would STFU, get out the plastic and buy the either the Tom Bihn Synapse 25 or the Synik 30 because the Synik bag can do EDC and 3-5 day business casual, 1 bag travel given its full clamshell opening and slightly bigger size relative to the 3/4 zip Synapse 25.
Edited to add- I find it extraordinarily difficult to believe that between the regular priced items on the Osprey website and the clearance section I linked, you CANNOT find a pack that would work just fine. I would note that even in season Osprey packs, when not on sale at the factory site, can often be found on sale at the usual suspects to include Amazon, REI, Moosejaw and Back Country.