When you say studs, I assume you mean screws? The base cabinets can be installed using EITHER a ledger board set level on the wall for the bottom back edge to rest on, OR with the two legs in the back. Not both. You would use the front legs in either method.
The base cabinets have two locations, at the top left and right corners, where you attach them to the wall. These are not required to be in studs, if you happen to have a stud in the right location that's great, but if not, the screw in anchors will be fine. The stability comes from the legs and from ganging them together.
The wall cabinets use the suspension rail and attach at the top left and right back corners with a bolt/nut fastening system. The PERFEKT units do not use the rail. The tall pantries use the base cabinet system
IIRC. The wall cabinets have a little lip on the back bottom to accomodate the space needed for the rail, so the cabinet hangs plumb.
The ikeafans website (not the forum area, the main site) has a streaming DVD of the installation process that might be helpful to you.