Welcome to the forum.
Aperture priority is still an auto exposure mode. So it will give you the same exposure as the full auto mode. You do get to choose the aperture, which affects your Depth of Field...but I don't know how much difference that would make when you subject is 50 yards away.
Shooting on a tripod will usually give you better image quality..especially if you do it correctly and use a remote release or the camera's self timer (to ensure that you aren't touching it when it fires).
Also, using a tripod to keep the camera steady, means that you can use a longer shutter speed without having to worry about blur from camera shake...so if you wanted a deep DOF you could set a small aperture (high F number). The smaller the aperture, the longer your shutter will need to be to compensate...and that's where the tripod really helps.