When you get down to wide angle zooms, the difference between FF and crop with regard to lens design and construction is huge. Meaning, if you buy FF, 16mm is the standard wide end for zooms. There are others that go down to 11, but you start talking about large lenses and real money to get one that doesn't have massive distortion. The angle of view difference between 11 and 16 is way bigger than say 30 and 35.
If you stick with a crop lens design you can get down to 10 mm in a relatively compact design for way cheaper than the 11mm FF equivalent. Canon makes a couple of well regarded 10-something crop zooms. I can never remember which is considered the better lens.
I suggest forgetting about FF for now.
For architecture, distortion free and corner sharpness will be your primary concern. Wide apertures are generally not needed for either architecture or landscape.
PSA: The above post may contain sarcasm, reply at your own risk | Not in gear database: Auto Sears 50mm 2.0 / 3x CL-360, Nikon SB-28, SunPak auto 322 D, Minolta 20