I did the "ultralight travel" thing with my partner in 2018 for a 3-week trip to England and Europe and a 2-week trip to Japan. In short: There were times we were really happy all we had were our backpacks, and there were times it would have been nice to have "that one thing, that one time," but it wasn't the end of the world. Given the fact that we were in Europe and Japan, it's not like we couldn't run to a corner store for anything we really, really needed.

Both times I took the same 19-liter backpack. The primary thing that this did for me is it forced me to be very selective about exactly what it was I really needed to bring with me. I bought the latest and greatest cell phone with the best camera on the market, and I used the phone for all pictures, navigation, and all the great things modern phones do. All guides were in the form of audio files that I would play through my Bluetooth earbuds. I was able to pay for almost everything using my phone -- except the Tokyo subway. (Seriously, Japan, let's get with the times).

The cell phone pictures turned out just fine. Sure they weren't emaculate works of visual art you might get from a dedicated $1k camera with interchangeable lens and what not, but they were more than adequate, and it was really easy to just whip out the phone and snap a picture no matter where we were or what we were doing. That ended up getting us some really ad-hoc pictures that added a ton of character to our trip album. Look back on the pictures now, I really have no regrets about that, and I still wouldn't add a separate camera to my (very parsimonious) list of things to stuff in the backpack.

For each trip I had 5 pairs of undies, 4 pairs of Merino wool socks, 3 Merino wool tshirts, 2 pairs of board shorts, 1 pair of pants, and 1 pair of shoes. I brought a few ounces of liquid detergent, which at one point put me in a ridiculous position where I was washing my clothes in the sink of a ritzy downtown hotel in Paris. I had a combo battery/USB Anker charger that works on 120v and 240v circuits with some plug adapters. Worked fine everywhere in England, Europe, and Japan. No laptop -- the phone can run a terminal app just fine if I really needed to SSH home for whatever reason. And I'm not going to be wanting to bang out novels or anything while I'm traveling. (I did buy a Logitech Bluetooth keyboard ahead of time just in case, but I ended up deciding it wasn't worth the weight and space). Google Fi for the carrier, which worked great and was cheap. A synthetic down jacket and GoreTex shell took care of variations in weather, and they both compressed down to fit in one of the zipper pockets. Carabiner clips ended up being pretty useful once in a while. Bought an umbrella from a corner store in whatever city I was at if I felt I needed one.

Both going there and back I'd get flagged for a manual bag inspection at the airport. I guess traveling overseas with no checked luggage is a security flag? The worker would open the zipper, see the top part of a compressed mass of clothes, shrug, and then close it up again. I didn't care about the "boarding crunch" to try to jocky for overhead space. The backpack easily slid under the seat in front of me with plenty of foot-room too, although I'd just pull the backpack out after liftoff.

While the backpack had only 19 liters of volume, it was pretty dense, and so carrying it around for more than an hour or so would start to get tiring. The padded waist clip helped, but occasionally there were times I wouldn't have complained if I could set it on the ground and wheel it for a while. But then there were times in train stations when we would zip around tourists heaving several huge suitcases around and jockying for space to put them on the cars. When we stopped places on the way to the hotel we never had to stress out about leaving our stuff in rental cars to get stolen. Just grab the backpacks and wear them to wherever we were going. Most of the time, we would unload all the extra clothes at the hotel room and head out with mostly-empty backpacks at our destinations.

One time we decided spur-of-the-moment to watch a play in London, and the only shoes I had were my black sneakers. I had a button-up synthetic shirt (rayon and cotton I think) and a dark pair of pants, so I mostly "fit in," as long as you didn't look to closely at my feet. But at the end of the day, I didn't really care that much, and I wouldn't have tried to haul around multiple pairs of shoes just on the off-chance I'd want to go to the theatre and be "completely" dressed up.

In short, I'm hooked on the 19-liter backpack way of traveling. The space and weight scarcity really forces you to be thoughtful about exactly what you really need to take with you, and you can focus on the experience rather than stress out about all your stuff. (I'm sure there's a broader analogy that can apply to all of life here.)