I fly carry on only or personal item only a lot.
An important key is first knowing how strict the airline will be with baggage sizers - a lot of them are cracking down now. Bags that will EASILY fit under the seat will not fit in the personal item sizer. My Gregory Border 35L was basically the ideal travel bag - perfect fit under all seats - but won't go in the sizer when it's packed. Find yourself a bag that has a fairly smooth exterior so it slides in the sizer without getting snagged. This is a
good example of one that's a good idea and
this is an example of a bad idea.
By the same token, for overhead bin carry on, just get yourself an Osprey Porter 46, is my advice. Best travel pack there is. All the straps stash away to make it really easy to fit in the sizer provided it's not super overpacked and the compression straps allow you to fit a
lot of stuff.
To fit more stuff, do not buy packs with a lot of internal organization or dividers - get a pack with a large, open compartment. Then use compression cubes / bags like these:
https://unluggage.com/collections/ea...packing-system
I had a longer response with examples linked but I lost it so here's the shrot version. Get a 20k MaH power bank and MAKE SURE it has the right output to charge your laptop (65W is what I use). Then get a mini power bank like the TNTOR ones on Amazon that easily charge your phone while it's in your pocket. Then get an Anker GaN charger that you can bring in place of your laptop's stock power brick. Those three things will save you tons of space on tech.
I suggest wearing leather boots with a vibram or similar sole to travel so you don't need to pack an extra pair of shoes (unless you really need dress shoes in which case I'd wear those to travel and pack some minimal sneakers that don't take up much space). Get a jacket that is versatile re: temperatures (i.e. OK from +10 to -10) with large pockets that you can use to carry your water bottle etc. on your person so you don't have to fit it in your carry ons.