I went through this exact same thing before a backpacking trip through the UK a couple years back. I was so sick of my bags being heavy with glass and fumbling with caps while it was raining. I ended up picking up the Tamron 18-300mm f/3.5-6.3 Di III-A VC VXD and it really changed how I shot... didnt miss a single candid moment. But honestly, you gotta be a bit careful with that 40MP sensor on your X-T5. It really pushes these all-in-one zooms to their absolute limit and you might notice some softness at the extreme ends if you arent careful with your shutter speeds. One thing I learned the hard way... make sure you check the firmware as soon as you get it. I had a similar lens act all glitchy with the autofocus until I updated it. The 18-300 is usually around $699 so it fits your budget perfectly. Just watch the weight balance on the X-T5 body tho, it can get a bit front-heavy after a full day of walking through European streets.

Honestly just go with Tamron for this. Their whole Fuji lineup is absolutely incredible right now! I spent a week geeking out over the MTF charts and the technical specs before my last trip to Italy and the real-world results were just as sharp as the data suggested. The way they handle chromatic aberration across the zoom range is honestly a masterclass in modern lens design... its just fantastic! I remember being in a dimly lit cathedral in Florence and the AF motor was just so snappy and quiet, even with the weird lighting. The engineering they put into the weather sealing is such a huge peace of mind factor too. Basically, just get any of the Tamron all-in-one zooms and you wont regret it. The X-T5 sensor really brings out the best in their glass and youre gonna love having that kind of versatility without the bulk of primes!

Just throwing this out there... Honestly, after years of hauling gear across different continents, I've actually moved away from the one-lens-to-rule-them-all approach. Those superzooms often trade off way too much in low light, at least in my experience. I remember a trip to Prague where I only brought one versatile lens and ended up frustrated every single evening. The glass just couldnt handle the narrow, dark streets without everything looking grainy. My current strategy focuses on a two-lens distribution instead. By keeping a tiny wide-angle in a jacket pocket and a standard zoom on the body, the weight is better balanced and the optical quality improves significantly. It sounds like more fumbling, sure, but it changed everything for me. Cost-wise, it's often cheaper to buy two solid mid-range options than one high-end superzoom. You get better results when the sun goes down too. Just some food for thought before you commit.

Ive been digging into the MTF charts for the Fuji-mount glass lately and honestly, going with Tamron is the move here. They have a really solid reputation for balancing chromatic aberration and sharpness on those 40MP sensors without breaking the bank. Last year I was traveling through some pretty humid spots and my budget lens from another brand basically gave up, but the build quality on these modern third-party zooms is a totally different game now... Before you commit tho, are you planning on doing mostly architecture stuff or more general street photography? It makes a huge difference for which focal range you should prioritize. I remember being in a tiny village in the Alps and wishing I had more wide-angle coverage, but then in Paris, I was constantly wishing for more reach to grab detail on the buildings. Tamron is definitely your best bet for staying under that $800 mark while still getting decent resolving power, just gotta figure out which end of the zoom range matters most to you.