I went to read up randomly on Sony vs Nikon mirrorless and came upon a Reddit thread which disses Sony ergonomics, non-intuitive menu and colours.
I am particular about colours so I went to read up more on Nikon mirrorless. I saw some great reviews on and impressive images from Z5. However, it’s a full frame. I don’t know if it would be difficult to use a full frame, coming from a DX user.
Nobody used Nikon mirrorless here?
If you want light weight and color science, consider Fujifilm X-T series. Light due to APS-C sensor, with Fujifilm's own interesting color science technology.
Sony was the first to start going mirrorless, so you can find a lot of Sony and 3rd party lenses for Sony's e-mount.
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Nikon FF are similar to DX. Just higher specs and your existing DX lens will not fill the FF sensor so it's not recommended to bring them over.
Don't get FTZ adapter unless you have a lot of nice and expensive legacy Nikon glass that you wish to keep using. Since you were using DX I would suggest you sell those if you wish to move to mirrorless.
For Nikon FF you can consider the Z5 you mentioned, or Zf (retro style) if you have the budget. Zf is like "Z6 III" in retro style. Main downside of Zf is the lack of a proper native hand grip.
Z6 II for sports (a bit dated model)
Z7 II for landscape (a bit dated model)
Z8/Z9 if you earn $$$ from taking photos (^^)
Lens you can just carry a pancake 40mm f/2 for street photography.
Its best not to carry too many lenses when travelling.
IF you need more than one during your travels, the maximum you need is usually just 2 or 3.
For dedicated landscape photography, either 14-24mm f/2.8 S or 20mm f/1.8 S.
You can also use a all-in-one lens like:
Either 24-200mm f/4-6.3 VR (pretty lightweight but average performance), or 28-400mm f/4-8 VR for more reach (heavier and more expensive)
There are other better S class zoom lenses but those weigh a ton...
Skip the TCs (teleconverters) too.
Other specialized lenses will be up to your needs.
If you are unsure consider renting or borrowing cameras from friends to try out.
Good luck.