Ebar, I think AMO standard is bow length -3". So if you shoot a 60" bow, you should have a string of approximately 57".
The stock flemish twist strings from 3-Rivers Archery are economical and are not bad strings. They are sold by actual length, so I would twist your string up until you are pleased with the brace height, then measure it. Sometimes the strings come in a bit long, so if in doubt I would go shorter rather than longer.
Within reasonable limits, brace height is a matter of personal preference. Personally, I am not a big fan of low brace heights. A relatively high brace gives a bit better clearance for bulky clothing, for example. The thing is, a high brace height will make stiff arrows act more limber... so if your arrows are stiff, try increasing the brace height. If they are too limber, try reducing it. Modest changes in brace height can accomplish quite a lot.
Good luck!