Comparing 16mm and 28mm is a huge difference. The KM 28-75 on APS-C is not wide at all. Try restricting yourself from shooting 28mm and below, see whether you're comfortable with it.

If you're into portrait, IMO... 135mm would be a great addition, it's down to personal preference.

IMO the CZ24 f/2 is not that attractive. At 77mm filter thread, the aperture should be below f/2.

At first impression, I thought those photos at SAR are edited from 50mm f/1.8 SAM lens. Was hoping for it would be either f/1.8 or f/2 instead of f/2.8. The 85mm f/2.8 SAM seems to be a good cheap alternative compare to the CZ85, and at 55mm filter thread + below 200 grams + small in size, it's quite pocket-able I think.

But if it's priced near Tamron SP90, might as well just go for the Tamron?

Not exactly,but closest to the human eye.
APS-C = 35mm
Full Frame = 50mm