Something to consider for the underseat bag, and I don't know if this applies to all airlines, all planes, or just this one model plane on this one airline - my bag I use for my computer is too wide to fit under the seat in front when I sit in an aisle on Southwest. The frame is a LITTLE narrower and the bag is too wide. Southwest is an all-737 fleet so other plane models may be different. As I usually travel alone (for work and leisure), I can't just ask my travel mate to swap bag placement to put the wider bag under the middle seat.
fortunately, this isn't an issue when I travel for leisure - I have a different bag for that as I don't bring my laptop usually. The bag I use won't fit the OP's needs, but just adding something I've observed.