Not suggesting you leave Nikon at all. Stick with the brand you prefer.
FYI, Sony A7RIV, A7RIVa and A7RV all have fullframe 61mp sensors, and Sony has a new 20-70mm f4 lens out now too.
DPReview:
https://www.youtube.com/watch?v=TsGj9DtOlswFull disclosure, I own the 61mp Sony A7RIV and it is super for landscapes. I am sure that 45mp stacked BSI sensor in both the Nikon Z9 and Nikon Z8 also has excellent IQ, resolution and detail for landscape shooting and enlargements.
When I need fast 30fps, blackout-free EVF, AI tracking, best and fastest AF, huge buffer, 1/32000 second shutter speed, true silent shooting with reduced rolling shutter, and more like 8k video recording (although the new 61mp A7RV now also does 8k recording) , then I reach for my Sony A1 with its 50mp stacked BSI sensor.
Just a few of the countless landscape shots I have made with my 61mp Sony A7RIV and my Sony, Sigma and Tamron native E-mount lenses.
1) Golden Gate Bridge, San Francisco, California, USA
2) Yosemite National Park, California, USA
3) Horseshoe Bend and the Colorado River, Page, Arizona, USA
4) Venice Beach and Pacific Ocean, California, USA
5-7) Monument Valley, Navajo lands, Arizona/Utah border, USA
8) Las Vegas strip, Las Vegas, Nevada, USA
9) Grapevine Lake, Texas, USA
10) Palace of Fine Arts, San Francisco, California, USA.
Cheers and best to you.
Not suggesting you leave Nikon at all. Stick with ... (