Would this Work?

I'm looking at buying the Black Herschel Classic Backpack XL 30L. My main requirements are simple. I want a bag that can fit all my things on any domestic trip and maybe even a few international ones. I want it to be as minimalistic and aesthetic as possible. I really would like it to fit underneath the seat as a personal item on any domestic flight. I don't carry much usually, one 14 inch laptop , 2 pairs of Jeans and a pair of Khakis, 3 shorts, 5 T-shirts, A flannel, 2-3 sweaters, 7 pairs of socks and briefs and maybe a pair of sneakers. I also carry a small toiletries pack. My question is would a 30 Liter bag be sufficient for this and filled would it still be able to be carried as a personal item? Should I go smaller or is 30 Liters a bit better in terms of future proofing for longer trips? Most of my trips are 1-3 weeks in length btw. Does anyone have any experience with this bag and do you have any other recommendations?