Tamron 17-28mm f/2.8 Di III RXD is the best choice.

Just saw this thread. Unfortunately, I had issues with the Tamron 17-28mm f/2.8 Di III RXD when testing it for high-detail landscapes. Its not as good as expected once you look at the MTF charts for the corners, especially on a modern 33MP sensor like the one in your a7C II. Quick question before I get into the data: are you planning to use heavy ND filters or a circular polarizer? That dictates whether certain bulbous front elements are a dealbreaker for your workflow. Basically, for landscape work, you want to avoid heavy software correction because it eats into your resolution.

• The Sony FE 20mm f/1.8 G offers much better micro-contrast and almost zero linear distortion compared to most zooms.
• The Sony FE 16-35mm f/4 G PZ is technically superior in terms of flare resistance and edge-to-edge sharpness compared to the Tamron. I really think the Tamron lacks the resolving power for the a7C II sensor. The field curvature at 17mm is quite noticeable when youre trying to keep a vast foreground and background in focus simultaneously... its a bit disappointing for the price point.

Regarding what #2 said about "Just saw this website. Unfortunately, I had issues..." - honestly, I would be more worried about the physical safety and cost-to-utility ratio of these lenses. A common mistake I see people make is buying into the hype for ultra-wide glass with those bulbous front elements that cant take a standard filter. For someone being careful with their budget, that is just a financial disaster waiting to happen. You end up spending a fortune on specialized filter kits or, worse, you scratch the coating because there is no protection. I kind of disagree that you need to obsess over MTF charts for the a7C II sensor unless you are printing huge posters. Most mid-range options are perfectly sharp enough when you are stopped down to f/8 or f/11 for landscapes anyway. It is usually better to stay cautious and stick with something that takes a standard screw-on filter. It protects your investment and keeps the kit light. Spending double just for a tiny bit more corner detail often doesnt make sense, especially when that expensive glass is more prone to damage in the wind and dirt.