I haven't seen enough of this video being shared around.
I was pleasantly surprised to find these highlights because there are tons of intermediate/deep throws in this video. A strong arm helps, off course, but for Alex Smith it looks like accuracy totally gets the job done. Having Vernon Davis all those years (and some Michael Crabtree) certainly helped Alex in SF but I'm sure the Chiefs can provide some weapons of their own.
Also I wanted to point out that Alex Smith is one of the most intelligent players in the NFL (for example, here and here). Doesn't Andy Reid have one of the most complex offensive systems in football? It has potential of high success if utilized correctly. I'm sure being a smart QB will help with that (and being exposed to 7 different offensive coordinators probably enabled Alex to retain quite a lot of knowledge of which good things can be retained from each system)...
Finally, good luck KC! After the trade (I'm a niners fan), I found out more about the Chiefs- now quickly starting to like them, will definitely be rooting for you guys!