Beef cut names can be very regional, which is confusing. Not to mention annoying.
A "sirloin strip" is taken from the top loin, not either slrloin primal. It also goes by the names, "hotel steak," "Kansas City strip," "New York strip," "stripper," "top block," and maybe a few other names.
The steak is less well marbled than a rib steak, and not as tender either. Although not one of the more tender steaks, it's definitely tender enough to be served as a steak. That is, by simple grilling without much elaboration. It's quite flavorful. The muscle structure has a pronounced grain. This means that after cooking, you should plate by slicing across the grain, presenting the slices "shingled," rather than serving each guest a whole steak.
In my opinion, the ideal preparation is the so-called "Santa Maria" style, just as you would cook tri-tip or a thick cut of top sirloin. Cut your steaks approximately 2" thick. Marinate, only briefly, in a tablesppon or two of marinade made from equal parts of worcestershire sauce and red wine. Just before grilling, season with rub made from kosher salt, pepper, granulated garlic, and onion powder. Grill both sides over high heat until just seared. Move the steak to a slower part of the fire (and/or cover) and cook until the steak registers 120 deg at the center. Allow to rest at least 7, but no more than 13 minutes before slicing and serving.
If serving as sandwiches, slice at 1/4" or less, and serve on sourdough bread or rolls. If serving as dinner, slice at 3/8" to 1/2" or more (if very tender). Again, always carve across the grain. The traditional accompaniment at a Californa barbecue is a fresh salsa such as pico de gallo.
Hope this helps,