This is really interesting. I live in a tourist town overseas (from my perspective as an American), and I've done a fair amount of travel, though mostly just in North America, Japan, and Europe. I've never had a fancy backpack or any special gear. Typically I bring an ordinary backpack that can fit under the seat in front of me, a rolling carry-on bag, and maybe an empty fabric or canvas tote bag inside one of the other bags. If I pick up stuff along the way, the carry-on bag can be checked and the tote bag becomes a personal item for under the seat in front of me. The tote bag can also work as a pocketbook or a shopping bag on a day when the rest of my stuff is stored. If I get tired of carrying the backpack, I can put it on top of the rolling bag and wrap the straps around the extended handle. I try not to pack more than I can easily carry up and down a few flights of stairs and walk with for a few miles.
If I'm between hotels and want to go light for a day of sightseeing or walking or for several days of lighter travel, I put the rolling bag in a locker at a railway station or airport. I've done that in London, Tokyo, and Bangkok. In Taipei I left my bags at a hostel and then at a hotel. Most major cities will have some sort of luggage storage service, and some hotels or hostels will let you leave things for a day if you are / will be / have been staying there.
Have you done a lot of backpacking? I'd think you'd want to do a bit of traveling in that manner close to home and with borrowed gear before committing to doing it for months in a foreign country. If you try it and you like it, that's great and you have lots of suggestions in the thread for good backpacks. Personally, I would get tired and grumpy after a half hour with a big backpack.
Whatever you do, check the airline's rules about bags. They change all the time and allow much less than you might hope. Here's Wow's rules for flights (including trans-Atlantic flights):
https://wowair.co.uk/customer-service/faq/luggage/how-much-hand-luggage-can-i-take-me/Wow allows one small personal item. That's it, even on international flights. If you have to add a carry-on at the airport, it's almost $100 extra each way. If you pay online for the carry-on ahead of time, it's still almost $50 extra each way. Just crazy, and it adds up.