p.2 #2 · Getting back into landscape photography with the a7r series
For your use I would go for the r3. I only upgraded mine to the R5 because of the highly advanced AF in comparison. If you use manual lenses and mostly landscape then it is still an ideal choice. That said it's AF isn't bad for portrait work as Eye Af works pretty well
p.2 #3 · Getting back into landscape photography with the a7r series
Whether I am doing macro or the occasional landscape, I use Focus Peaking a lot and I find the A7r or A7r3 one significantly less helpful than that of my Olympus EM-1 (1).