The Canon EOS Rebel SL2 has the identical sensor (and sensor performance) of the EOS Reberl T7i. The major difference is that the SL2 doesn't have the same focus system and is physically a more compact EOS body (it's the most compact of any DSLR).
Higher end focus systems usually are loaded up with many more focus points... which is great for tracking fast moving action. Macro and landscape photography typically don't have fast-moving action... so this is a feature you are unlikely to miss.
The EOS 5D Mark IV is a high end full-frame body (not quite the "flagship" Canon body, but it's up there). The EOS 6D Mark II is considered an "entry level" full-frame camera ... but don't be disuaded by the term "entry level". A full-frame body typically costs in excess of $3k. This was a camera that Canon designed to cost less than $2k in order to make "full frame bodies" accessible/affordable to those who just can spring for cameras in the normal $3k+ price range.
The SL2 body is about $550 (for the "body only"). But if the only lens you have is the 180mm macro (which is a VERY nice lens... possibly the most sought-after macro lens) then I'd probably get a "body+kit" version so you have at least one general purpose lens. The body with the 18-55mm f/3.5-5.6 IS STM lens is about $650 and an 18-55mm focal length would work well for landscapes.
A 6D II "body only" is about $190. With a 24-105mm "kit" lens (which gets tricky because Canon has a few different 24-105mm lenses right now) it's about $2400 with the variable aperture version, about $2800 with the latest 24-105mm f/4L version II. The 16-35mm and 17-40mm zooms would also be good landscape choices.
Usually (but not always) landscapes are shot with moderately wide angle lenses. This is because a side-effect of "wide" lenses is that they "stretch" the sense of depth and make a scene appear deeper and bigger than it is in real life. Just occasionally a landscape photographer will use a long focal length lens becuase they do the opposite... they create "compression" which creates the illusion that things are closer than they really are.
This shot was taken with a 70-200mm at about 155mm focal length (using a full-frame camera) because I wanted to narrow the angle of view (to cut out unattractive distractions out of frame - as I recall there were road-signs to the left of frame and some buildings and parked cars to the right of frame) and also because I wanted the "compression" to allow for a bit more detail in the carpet of flowers. But this is uncommon in landscape photography.
If you aren't familiar with the difference between a "full frame" vs. an APS-C "crop-frame" camera, the sensor size of the "crop frame" camera is a bit smaller. This means more of the image being projected into the camera by the lens spills off the sides of the sensor and isn't recorded. It produces a narrower angle of view than what you see if you used that same lens on a "full frame" camera body. A "full frame" sensor meassures 24mm tall by 36mm wide. An APS-C "crop-frame" sensor measures 15mm tall by 22.5mm wide.
But it's the impact of having a physically larger sensor means the photographer can position the camera a bit closer to a subject to get a similar composition. This change in position alters the depth-of-field for the shot, which in turn increases the amount of background blur. Photographers who do portrait photography (or just want a burred background) usually enjoy the effect.
