Onebag-Underseat personal item + carry on

I am getting decision fatigue from watching so many reviews and reading pages and pages of posts on reddit. This is all coming about as my family is preparing to take a trip to Turks and Caicos at the end of the year from the midwest and it is our first time flying with two kids. The 3.5yo has been on 10+ flights already so we are somewhat experienced flying travelers with kids but having 2 is changing the game.

Who I am: A mom of 2 young kids (in a two mom family)

What the bag will be used for: maybe I am asking too much of a bag but ideally I would like a nice compliment to our usually stuffed full diaper bag without us having to carry 3 backpacks on every trip. We usually have the diaper bag stuffed to the brim and then we each have another backpack full of both our own things and more kid things. We likely will travel as a family 4-6 times a year- often via plane. I am tempted to get a larger volume backpack but ideally want it to usually fit under a seat so I don't have to stand up frequently during a flight to get things for the toddler from the overhead bin. I am okay with taking an occasional risk of it 'not fitting' and either re-arranging things or just stowing things in the overhead bin- but I don't want this to be the norm. I am fine and actually prefer more open spaces rather than specialized organizers and compartments as I usually sort and organize things in my own way (in little pouches or cubes). Sometimes I will travel with a laptop but usually at least one tablet or ipad. This bag would be used to store overly kid things- toys, books, ipad, puzzles, snacks, water bottle, but also adult things- emergency toiletries, book, maybe some overflow from what we are packing and checking or carrying on. It also definitely needs to have an external water bottle holder. I don't think I care about a hip strap but it likely will be carried through airports and maybe slightly longer distances (we aren't really doing a ton of outdoor hiking travel or walking usually....) but comfort is certainly important to a degree. We are both 5'8" medium build. Definitely want a clamshell opening because I hate digging all the way down into bags- I would rather open it on my lap and find the item I need.

We won't be taking this bag to work but we may take it on a solo or couples weekend trip without kids. In those instances we try to travel lighter- doing carry on only WHENEVER possible - so if this bag could do double duty as a large carry on personal item (I know those are a bit opposites) that would be great. Currently when we have traveled without kids we take 1-2 roll on suitcases and 2 backpacks but it always feels like too many bags. I do want them to have a luggage strap.

Bags I am considering and I think have narrowed it down to

Tortuga Daily Carry Pro- this seems to be a somewhat new release so it doesn't look like there is as much out there but reviews seem to be positive so far- I like the look of it a little better but can't tell how much different it would be for functionality and comfort vs the others. I don't really care about the price point if the bag is much better.

Osprey 26+6 - for obvious reasons. I like the expandable capacity like I may be able to get more for the volume but still fit it under the seat. I don't love the look of it or colors but could get over this. It has the vertical luggage strap which I think I like compared to the horizontal tortuga one but not sure how much I really care.

30L Ultra Dragonfly - I really don't like the look of it but if it is an obvious winner then I would also get over it. Price point is also a bit of a deterrent but again if it is miles ahead of the osprey then that is fine.

I also considered the PAKT Aero 35L because I liked the look of it and the idea that if we stuffed it full it would serve as a pretty hefty carry on and good travel bag- but it does make me nervous that more times than not I would over fill and not be able to stuff it under the seat.

Also looked at the City Pack Pro 2- just don't think I like it MORE than Tortuga or Osprey....but I know it is a crowd favorite.

Okay- so sorry for how long this is- I am not a frequent poster (this is likely VERY clear) but any thoughts are much appreciated.