You should avoid playing games on any wireless. You want to use ethernet cable. Only as a very last resort should you use wireless...it will mostly work but you will get the random stall and disconnects that come and go.
You have 2 choice...well 3 if you look at bridges... You can go with a internal PCI card or you can use a USB based device. The Internal PCI card many times offer more option for things like mimo. This is mostly because its easier to put antenna on them that have the proper spacing for mimo to work. Now do you need mimo ? Mimo give 300m where a non mimo card can only do 150m. There are a small number of USB card that can do mimo. The key difference I see is that the USB you can place on a long cable with no loss of signal. It allows you to place it in a strong signal area away from the computer. The internal PCI card have the antenna directly attached to the back of the card. This places them very close to back of case which blocks signal, and then if you put it against a wall it blocks even more. There are extension antenna that allow you to move them to the top of the case but you tend to lose a lot of signal in the wires unlike USB.
Again go with ethernet cable even if it means you have to work at to hide the cable to keep the wife happy. You will get much more reliable gaming.