If you will be using a single speed freewheel, then you will want a rear brake. Assuming the rear is a rim brake (not disk), then you want forward facing semi-horizontal dropouts, so you don't have to have to readjust the brake pad position every time you change the position of the wheel in the dropouts. Also, you won't need a chain tensioner or eccentric hub / BB as you would with vertical dropouts. I have lots of bikes with semi-horizontal dropouts and both quick releases and axle nuts, and I've yet to pull a wheel. It also makes it easier to remove / install the wheel if you have full fenders. For road use w/o a disk brake, just get a frame with 120mm spacing in the rear dropouts and you will find it easier to find wheels that will fit with a SS hub.