For your situation, I would suggest really looking at the used market to save some serious cash while traveling. I have been doing this for a long time and honestly, reliability is key when you are miles from home.

• Sony E 18-135mm f/3.5-5.6 OSS
• Sigma 18-50mm f/2.8 DC DN Contemporary for Sony E
• Tamron 17-70mm f/2.8 Di III-A VC RXD The Sony 18-135 is basically the best value at around 350 to 400 bucks used, but be careful with it at night cuz that slower aperture might force your ISO way too high. I once shot a whole trip with just this and lowkey regretted not having something faster for evening street scenes. The Sigma is tiny and sharp, but you lose that reach. The Tamron is just too bulky for hiking imo, it will make your setup front-heavy which can be risky for your wrist. Make sure to consider grabbing the 18-135 used and maybe a cheap Sony E 35mm f/1.8 OSS for low light. Best of both worlds without breaking the bank... gl!

I definitely agree with the point about constant aperture. It makes such a difference when youre zooming in and out while tracking a subject, especially for travel video too. Basically, it just takes one more thing off your mind while youre exploring. Heres a couple quick tips to keep your budget in check:

• Keep an eye out for a used Sony E 16-70mm f/4 ZA OSS Zeiss. Since most people are chasing the f/2.8 zooms now, you can find this lens for a steal. It is super light and fits the a6700 size perfectly without being front-heavy.
• If you really want that all-in-one reach, the Tamron 18-300mm f/3.5-6.3 Di III-A VC VXD is worth a look. It is basically the ultimate travel tool if you dont want to carry anything else, and it is usually cheaper than buying two separate zooms. That 16mm wide end on the Zeiss is actually a really big deal for landscapes compared to 18mm lenses... definitely something to consider if you do a lot of scenic stuff. Just a thought since you mentioned street and landscapes.

So ngl I have to disagree slightly with the 18-135 suggestion. Its a decent kit lens but if youre rocking an a6700 you really want something that holds its own when the light drops. Variable apertures are just a headache for travel photography imo because your settings keep jumping around. I would actually look at the Sony E 18-105mm f/4 G OSS instead. Its a bit older so you can find them used for around 350 to 400 bucks which is insane value for a G-series lens. Here is why it wins for a traveler:

• Constant f/4 aperture so you dont lose light as you zoom in
• Internal zoom means the lens doesnt physically grow, making it way more durable for hiking and dusty environments
• The power zoom is surprisingly nice for video if you want to capture some cinematic clips of your trip The Sigma 18-50 is tiny but the lack of reach is real when youre trying to frame distant landmarks. The 18-105 gives you that extra bit of telephoto without being as massive as the Tamron 17-70. If youre trying to keep costs down while getting consistent results, its the way to go. TL;DR
• Skip the variable aperture lenses and grab a used 18-105mm f/4. It offers the best mix of reach, constant light, and budget-friendly pricing for the a6700.

Adding my two cents here because I went through this exact struggle when I first got into travel photography. I used to be obsessed with having the fastest aperture possible, thinking I needed it for every shot, but a trip to the Swiss Alps totally changed my mind. I was constantly fumbling with lens caps in the freezing wind, and I actually ended up missing a shot of some mountain goats because I was mid-swap between a wide and a tele. It was super frustrating. After that, I decided to prioritize reliability and range over everything else. The one I got was the Tamron 18-300mm f/3.5-6.3 Di III-A VC VXD for my Sony a6700 setup. Tbh, I was worried about the weight at first, but not having to expose my sensor to the elements in harsh conditions has been such a relief. Its survived dusty trails and some light sea spray without missing a beat. Having that massive range in one lens just lets me focus on the actual travel experience instead of worrying about my gear failing or getting dust inside the body. For me, that peace of mind is worth way more than a slightly wider aperture... really makes the whole trip more enjoyable.