I've been looking at the tilt/shift lenses for some time, and the ability to change the focus wedge is appealing to my geeky side. As usual, googling for which tilt/shift lenses are used for what, is just as futile as trying to drink from a firehose 
I guess that the 17mm and 24mm are primarily used for architecture and landscape work, and the 90mm for products (and that miniature effect). But what about the 45mm?
Since I am mostly thinking to use selective focus (tilt), I presume that the 45mm and 90mm are more obvious tools. However, since I already have the 1.4x and 2x (MkIII) extenders in, one option could be to use an extender with the 24mm, allowing me to dabble in architectual shots as well..
Looking at the local 2nd hand market, it seems that there are a bunch of 24mm, 45mm, and 90mm available for reasonable cost, but which focal length would be the obvious choice?
I have zooms in the similar focal length areas, but no primes yet. I'm (also) tempted to get the 100mm L-macro too, but that's a seperate topic.
Edit: I'm shooting on a FF camera (5D3).

I guess that the 17mm and 24mm are primarily used for architecture and landscape work, and the 90mm for products (and that miniature effect). But what about the 45mm?
Since I am mostly thinking to use selective focus (tilt), I presume that the 45mm and 90mm are more obvious tools. However, since I already have the 1.4x and 2x (MkIII) extenders in, one option could be to use an extender with the 24mm, allowing me to dabble in architectual shots as well..
Looking at the local 2nd hand market, it seems that there are a bunch of 24mm, 45mm, and 90mm available for reasonable cost, but which focal length would be the obvious choice?
I have zooms in the similar focal length areas, but no primes yet. I'm (also) tempted to get the 100mm L-macro too, but that's a seperate topic.
Edit: I'm shooting on a FF camera (5D3).