Let the game auto-configure the graphics by itself. It usually gets it right. You can install a tiny program called FRAPS (
http://www.fraps.com/download.php) which will show you the frame rate while playing the game. Mess around in the training room with FRAPS running to make sure the game stays at 60 fps all the time. Perform X-rays and flashy combos and so on. The game, unlike Injustice on PC, doesn't take that much from your machine so I don't think you'll have any problems.
For best pad experience, use Xbox pads or PS pads with Xbox converters (I'm pretty sure you got this covered since you play on XBL most of the time and go to tourneys.) This is because Windows has a native Xbox pads support (Microsoft) and otherwise you'll have to install drivers and/or emulators, and remap buttons inside the game, and you'll still face some weird stuff like having to use the Circle button to confirm and X to cancel. Nothing too bad you'll get used to it quickly but it can be a little annoying at first.
