The M 50 Macro, M 100 Macro and M 100/2.8 are all excellent. 105/2.5 Vivitar Series 1 AKA Lester Dine macro is also excellent but very large compared to the Pentax lenses, but does 1:1 magnification natively. My copy has a bit more resolution (who cares) but has more issues with color fringing on high contrast lines. If I was less inclined to limit myself to 1 lens when out walking/shooting casually, I would have kept the Pentax as it is much smaller and lighter, and if you include a set of extension tubes with the Pentax, it is just as large to pack along.
If you want to keep it very simple and don't need large apertures: M50 Macro + Vivitar 2X macro focussing teleconverter + whatever wide angle gets you the landscape/architecture view you prefer. The Vivitar 2X TC takes a normal 50mm and turns it into a 100mm 1:1 macro, albeit with the loss of some image quality and some light.