An alternative view. Do you really need a bag of this size? I think I've read you're off on a family cycling holiday so I appreciate it may well be necessary.
My approach has evolved over the last two years. This is for both our usual short rides, 50-60 miles, and "big" days out, 100+ often gravel. For shorter rides I use this Restrap bag for tools, snacks, glasses and rain jacket.
Canister Bag (1.5 Litres) – Restrap
https://share.google/y4s2KasoQnmuBuTbp
This can be a squeeze and sometimes I still have to use jersey pockets which I don't like. A few months ago I invested in Lusso Terra Cargo bib shorts. The leg pockets are ideal for a phone and/or items one wants easily accessible - snacks in my case. The big win with these bibs is the full width pocket across the back. It's ideal for rain jacket, gilet etc and I'm completely unaware I'm using it. The best rear pocket I've known.
Terra Cargo Bib Shorts
https://share.google/1o6asKMogkOpzjXtN
If all else fails I still have my tool pouch available to go under the saddle. I rarely use this in summer. It's a winter thing to create more room in the bar bag for winter clothing.
Tool Pouch (0.6 Litres) – Restrap
https://share.google/bxkVvXHEUTSCoNCGQ
I don't pretend this is a cheap option but it's one alternative to a large bar bag, something I would find very uncomfortable and limiting to use. I couldn't ride with such a large bag. While these companies are top of the price range I find their product quality, service and ethos more than justifies the prices.