With size 12, you will not be limited. I ordered five pairs of shoes from Bike Nashbar, with the understanding that I would be able to send back what I did not like.
I wanted something with regular soles that fit well. The SIDI were the only ones that fit well.
So, I keep a pair of walking shoes readily available in my panniers, so when I am forced to walk up long hills, it is more comfortable. Note, my vanity dose not force me to push me beyond my limits. Each year, after I start riding, the better I am able to climb. Still, when I am biking up a hill at 2.8 MPH and know that I can walk the bike up the same hill at 3.3 MPH, it makes more sense to push.
Regarding toe clips. I have tried them and did not like them. My wife love them. Try riding with toe clips and see.
The biggest reason for the clips is the extra help you get by lifting up with your feet when you peddle.