I really like the proportions of the 5x7 print. I have contact printed on regular enlarging paper as well as cyanotype, Van Dyke, platinum, gum and salt prints. The only way to find out which method suits you is to try them. Apart from the platinum, most are not expensive, (relative term, of course).
Cyanotype is probably the best to start. It's pretty easy and if you decide that you don't like blue, you can always tone it. ("How to" article on this very site.)